Another thought:
How about, instead of ranks for a command, we have aspects of the command that can be improved, independently.
So for stab you might have (remember these are examples!):
- how heavy a weapon you can use
- how well you can use an edged weapon instead of a pointed
- how fast you are at preparing to stab
- how well you can fight whilst preparing to stab
And for summonbeast:
- the range of animals you can summon
- the strength of the animals you can summon
- the need for a staff
- the need for a herb
Each aspect would start at rank 1 and be raisable to rank 4.
You'd probably have a max number of raises for any command, say 10. The difficulty of raising an aspect being dependent probably just on the rank of that aspect, not how many of your 10 you have used up, but maybe that as well.
This would allow for a wide variety of choice for players and result in players being different from each other, rather than everyone just having all things maxed.
Compared to the discussion above:
It makes more sense in that as a player you can concentrate of the bits that you want most rather than having to work through 10 ranks for the whole command when all you really care about is getting the stuff that rank 6 gives you.