I have had some of the same thoughts with a few of my characters concerning MA.
Some considerations:
1. If you are going Adrenal Defense rather than armor then MA will allow you use of the weapon kata.
2. MA is normally raised for each rank. Rank 1, Rank 2, Rank 3 and Rank 4. So you kind of need to raise all of those skills each level - UNLESS you focus just on using Adrenal Focus 1. Then you can use the Rank 1 (with Body Weaponry) and do damage off the Mace table or your 1-handed weapon. Here you might not develop Directed Spell skill in anything but Adrenal Focus 1. And you won't get Adrenal Focus 2, 3 or 4 until later - so you can't develop ranks in direct spells until later - so they will have much lower OBs.
3. The Adrenal Focus does require you to cast a spell, so that is your one spell per turn.
4. MA gives you an OB when you don't have a weapon, but then you are developing all 4 ranks unless you want your damage capped really low (unless you use Body Weaponry which you get at 8th).
So overall its a steeper investment, but I personally like the flexibility. The cheap route would be only developing Rank 1 MA and Adrenal Focus 1. But if you our out of Power Points (or prevented from casting) your damage will be capped pretty low.
If you go the martial artist route, then definitely look into the Talent or Background Option 'Martial Arts Training Greater' (RMSS) or 'Martial Arts Training' (RM2 - Companion 1) and Hammerhands (RM2 - Companion 1).
Mal