D&D 5E how would it hurt to take a diffrent class sub class

[practicalm]

Another way to approach it is like feats. You can get the Martial Adapt feat to get Battle Master type powers. It could be possible to create feats for different sub-class powers as well.

 

[DracoSuave]

Side note it looks like the there is a typo and the eldritch knight has one less cantrip... Strange.

Different classes can, for various reasons, have a different number of spells known. It may be because of the schools of magic involved as a balance lever. Minor Illusion, Friends, and Mage Hand aren't as effective in combat as Fire Bolt and Blade Ward.

 

[Rune]

I threw together some simple rules/guidelines for doing just what the OP asks not too long ago.

 

[Jester David]

Gaining the fighter options at the rogue's levels shouldn't be too broken. I might allow it in my game.

 

[transtemporal]

That's a pretty cool idea. If I allowed it, I would only allow it to replace your existing sub-class options i.e. you could take either Assassin or Battlemaster, not a mix and match of both subclasses. Furthermore, I would probably have a background requirement for the character e.g. Soldier for Fighter subclasses, Acolyte for Cleric domains, Criminal for Rogue subclasses etc. I wouldn't require a multi-class requirement though, that's too onerous.

And of course, it would be subject to some thorough scrutiny to look for broken combos.

 

[Uchawi]

I have been a strong advocate of a feature that allows martial characters to exchange ability from the beginning of the play test. You even saw hints of it in the initial playtest where maneuvers were present for classes like the rogue, fighter or monk. And then they decided to scrap it, and my entire interest in 5E started to wane. I believe it is going to be very hard to retrofit such a concept in the DMG guide, since martial class ability did not use the concept from the very beginning. Where casters have mechanisms built into spells to do the exact same thing.