Shattered Kingdoms

I'm not a fan of multi-classing either. Old school D&D is my bread & butter, and I didn't like the way multiclassing was handled in D&D either. I prefer a solid class-based system.

You have, on one hand, character classes who are called "useless" by various veteran players. But then you have, as illustrated here, players who want access to the abilities of those "useless" classes. Multiclassing essentially neuters the existing hybrid classes who are already a form of multi-classed character. If you open up the multiclassing as suggested here, class lines are effectively erased. Think rogues or bards are "useless" now? Just wait until mercenaries have access to their skillset. Rogues and bards would virtually disappear.

I understand why the heavily-customizable option is appealing to people. I played a handful of MUSHes back in the day that were designed around skill/spell choices instead of around classes, and they had some appeal, but ultimately they just led to every player pursuing the exact same build to acquire the exact same prime skills/spells.

However, I could be interested to see a variant of the multi-class introduced in the form of a low-level trade-skill apprenticing:
Low-level combat skills (ie- staff, shield block, rescue, etc);
Low-level cantrip spells (ie- detect magic, continual light, tongues, mend, etc);
Low-level craft skills (ie- tailoring, forging, fletching, mining, etc);
Low-level trade skills (ie- instrument-playing, ventriloquism, dancing, etc);

Tweaking the low-level abilities into a kind of pool for specialization can open up the opportunity for a lot of customization through a host of low level "useless" abilities and to introduce a host of new skills, including craft/trade skills. Nobody else needs access to magma spray or counterstrike. Access to reading/writing skills might be limited by unmodified intelligence; mining might be limited by unmodified constitution; etc.

This is something that I personally think would add a lot of really interesting customization options, even though they might offer little of interest to the hard-core power-gamers. I like to think of characters as a full package over the course of their life, including both solo and group activity, and both PvE and PvP activity. Many apprenticeship skills/spells could add a lot of interesting customization without threatening balance in regard to the big game-changing skills/spells.

To rebuttal some of your points:

If someone wants to play a merc and spend 300 LT's to obtain the magma spell, they should damn well be able to! Lol the dude would be a legend and would have to pay the price to be a legend! (I'm half-trolling here. But you get the point)

The skills/spells vs LT cost can be scaled depending on how OP it would make the class.
The skills/spells available to each class can be adjusted to avoid OP builds.
Perhaps additional skills/spells can only be accessed after your character's first age tick, promoting longer-lived, more versatile characters.

There are numerous numerous ways we can go about this. And in all honesty, as sucky as it would be to spend the LT's, I think a somewhat high LT cost is the place to start.

How about giving rogues the ability to make a set of lockpicks (not really any different than a vial, or scroll) that are a one time use that another player could use then? That way when they are not around someone could still actually progress into so many of the areas in game that absolutely require pick lock to be used?
Agreed, but multiclassing and gestalt in later editions was meant for low player count, when you only have a party of 3, its hard to cover the basics. An Elf in BECMI was already a fighter/mage and once players hit name level they could gain a focus into one area, that is how a fighter became a paladin, a cleric became a druid etc.
Sadly, you are probably right in this regard. However I am quite fond of bards, and consider them an absolute for any true adventuring group. (oh the things so many people have not the slightest clue about, because they did not have a bard along )

I agree, things that define a class should never be made available to the other classes. But there are cases where some abilities being accessible to others would improve the game (or at least I would think so), like a scout who could pick locks (why not have the 3rd adventurer class gain it as well), a priest who can cast healing rays (far better than mass healing), a mercenary who could learn to fletch their own arrows.
A trade-skill system sounds fine to me.
I think the options should be tied to each class, and I even if it did require your character to age a certain amount (half age across the board may be a little extreme in cases like elf/delf) I would still like the idea.
Possibly an either/or system so veteran players could purchase some options with LT's, but any player could gain access to them after a certain period of time on that specific character.

I disagree. I understand you're half-trolling, but that example for LT goes explicitly against one of the most important parts of LT - they are explicitly intended to NOT make your character more powerful. So tying LT into these scenarios that are about making your character more powerful are an immediate non-starter. Do YOU want to be PK'ing against magma-spraying, heal-casting, ethereal mercenaries?

If your desire is to use LT to make a more powerful character, your proposal is dead before it lives.

If your desire is to create the opportunity for expanded customization and specialization of your character, re-read my proposal. It's not likely to happen either way, considering how much code support it would require, but seems more plausible in terms of limiting OP variants.

The lower level items Yed spoke of were more of what I had in mind. There's no way a Merc with heavy armor and absolutely no mental training would ever be able to even think of casting the most powerful warlock spell but a Merc being able to ventriloquate or maybe even shrink items at most wouldn't be that far fetched. Again, the heavy armor would kill the abilities to poor at best but there's a chance.

The idea of creating more consumables is a good alternative to multiclassing in my opinion. Make the adventurers be able to create lockpicks. Pretty much every class should have a consumable they can create to offset their absence in a party. Not just casters.

And again, the "useless classes" would still be utilized by the players that do not want to make the commitment to earn LT's. Especially with a high cost. Gonna keep driving that point because I believe it.

The way I see it, if there were to be any spell-sharing going on between classes, those classes would have to be in the same sub-type. Clergy classes should only be allowed to obtain skills/spells from the clergy class, Adventuring, Warrior and Mage all the same. Still I think this takes away from people actually having to work with one another. I've already found ways to go to pretty much any endgame area with just two people. Allowing such blatant mixing of skills/spells then I think going solo through SK would be far too easy with the right class and 'multi-class' spell combos. This includes even keeping the skills/spells within the same sub-categories as I have mentioned above.

However, at least it would make sense if I lighty priest were to throw a bolt of glory, or a hellion casting harm. A mercenary casting magma or ethereal is too far at stretch in my mind. Warriors stick to their trade, Adventurers to theirs, Clergy to theirs and Mages to theirs. Anything more than that I believe would be too far a stretch outside their own comfort levels of spells/skills.

It doesn't make any sense to me to have what you're describing be tied to loyalty tokens.

@Yed,
You make a good point and it was something that I overlooked in regards to our LT policy. They shouldn't be able to make a character more powerful.

Imo, I think that making a character ever so slightly more powerful would be acceptable. But to make them God-like, I wouldn't ask for.

Your list of skills is pretty good. I'd like to evaluate all "utility skills" and see which ones would be applicable.

That's a good argument to improve those classes instead of giving away their key skills and making them completely irrelevant.