Hmm, now that I've looked closely at extra appendages and thought about it some, I think that the multi-maneuver part of it may actually be better than the multi attack part. Expecailly since you don't need any supporting powers (like claws or strength) to get a lot of milage about being able to lay multiple aspects on people with just one action.
I think that balancing that, along with balancing multiple attack at the same time may be difficult.
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Assupmtion: It would be impossible to balance multi-attacks in all circumstances since the the level of weapon you are using greatly changes the utility of making several attacks that hit with a low margin of success.
So, I think the balance point should be centeread around great base targeting with weapon:4, and that whatever solution is used doesn't outright break the system up to, say, fantastic targeting and weapon:8
So, we have:
-2 muliple appendages
Great targeting, weapon 4
If that's all we have, just gained the ability to spray attack with our claws (or whatever), and the seems to be it.
If we get one level of coordiantion, we can make 2 attacks at +3, or 4 attacks at +2 or our normal attack at +4, plus an effectively free attack at +2.
If we have 2 levels of coordination
Regular attack +4, plus free attack at +4 (same as two attack option)
Or four attacks at +3
If we have 3 levels of coordination
four attacks at +4
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This implementation of coordination is defenitely broken as it goes up in levels. Maybe change it to something like +1 to one spray attack per level, not to exceed the max? So that having coordination 3 gives you +3 in total, and not potentially +18 if you want to split your normally fantastic attack pool 6 ways. In theory, +1 attack for one refresh is balanced, so +1 to (one) spray attack should also be balanced, if a bit underpowered.
How's this instead:
Excellent coordination [-2]
When making spray attacks, add 3 to your skill before splitting your skill into the separate attacks of the spray. When the split is done, any single attack of the spray cannot be higher that your base accuracy.
And make multiple appendages give you point point of 'bonus pool' already. That means you are paying around 1.5 points for spray anything and spray maneuvers, and around .5 points for the +1 bonus to spray pool. And you can pay another 2 points for a +3 (so total +4) spray pool. So you'd be paying -4 refresh for what could amount to a free maneuver or attack at +4 every turn, in addition to your normal attack or maneuver.