Mystic Theurge Optimization

[Paleomancer]

Greetings, forum-mates!

I had two questions regarding the Mystic Theurge prestige class, and thought I might procure some feedback from this fine forum. One caveat: I am aware the Mystic Theurge is considered significantly less than useful, but the idea of the class intrigues me. As such, while I understand a common answer would be some variation of "don't use it," I was hoping for a more... analytical approach to the issue.

1) Because the class literally offers nothing more than dual progression in two or more spellcasting classes, would making it 14 level class be at all a problem? Assuming a default Wizard 3/Cleric 3 Mystic Theurge 10, access to spell levels seems unchanged until you would normally reach the cap at Mystic Theurge 10, but continuing on means you get a few 9th level spells at level 20. One would still be delayed in terms of spells, but perhaps this would make it more a choice of more spells versus powerful spells? I'm aware this is not allowed under RAW, but for the purposes of game play and house rules, is this a problem in any way? Potential balance issues I'm not seeing? Not matter because most people don't play at high levels or because it matters less at high levels.?

2) More general ideas of making the Mystic Theurge a solid option, without overpowering other classes entirely. Perhaps redesigning it? From a mechanical perspective, it's an intriguing challenge given the potential power of casters, but from a story perspective, a mystic theurge is almost more of an Archmage-type individual than is the actual Archmage prestige class.

[Kayblis]

1)It wouldn't break the game to make it a 14-level PrC. Some would argue it's even not a very good option to begin with, because you effectively have 20 levels of almost no class features at all. Sure, you get to a 9/9 situation, but you still have fewer 9th-level spells overall(3, one being a domain one), not to mention you have two casting stats and almost the chassis of a Wizard(same BAB, bad HP, small save bonus).

The biggest harm to the player comes because of the late progression. Yeah, by level 20 you have 9/9 casting, but up to 19th level you have zero 9th-level spells. You get your spells 3 levels later than other full casters. Your saves aren't as good. Your CON isn't as good. You spend more money on stats. Any level-appropriate spells are usually underpowered for you, and even the cheese isn't very strong. You won't break the game with more low-level spells, you still only have a standard action to cast and a swift action to burn effects on. Hell, you won't have much use for Quicken MM until much later, at the point others are on a level they're comfortable spending extra slots for mid-range spells. So no, you're all clear on making it a 14-level class.

2)The Ultimate Magus is an interesting approach, spending spell slots on one class to power metamagic feats on the other class' spells. I believe you could make something similar, but different - get rid of your biggest weakness, not being able to cast what you have. Make a class feature that lets you cast one Arcane and one Divine spell with the same full-round action, limited on uses/day. Start it on 1/day, and go up to maybe 5/day at 10th level. You can limit the spell level if you want(like, at least one of the spells need to be ~2 levels lower than your highest spell available for that branch of magic, or maybe both are limited like that). This means you can get out many weak spell effects and have your unique tricks and interactions between them as your main class feature.

Also, maybe give bonuses to CL at some intervals but only to CL checks, like dispels/SR bypassing/opposed checks. That is, if you think a straight CL bonus is too strong.

[Mordaedil]

I always thought they could have solved this by having the Practiced Spellcaster feats actually increase your caster level in all respects, also killing dead levels, so you'd be a proper effective 16/16 caster by level 16. Raising the level cap from 10 to 14 would help maintaining this too. Or even just raising it to 12 and let the two feats of practiced spellcaster cover the rest would be a decent invest-return as far as I'm concerned.

Sure, you are a proper level 20 caster in two classes, but you spent 2 feats getting there and probably had a few levels you struggled.

[bean illus]

Just easing the raw debate on the prereq "second level spells" to mean 'a second level spell in a divine and an arcane base class', would bring the caster progression to -1 spell level behind in the primary class, and -2 in the second class.

X1/Y3/MT10 then gives 7/6 casting. It also gives you 6 more levels to reach 9th level spells.

Here's a list of most of the arcane advancing prcs.
http://www.giantitp.com/forums/showthread.php?405416-Prestige-Classes-with-Full-Arcane-Spell-Progression

MT is supposed to, and should, advance behind wizard, and there's nothing wrong with it not being the most powerful. Just allow early entry at the cost of 1 feat.