Tested BG2EE /v1.2.2030 (and can be applied to BG1EE v1.2).Observed behaviour:
1. You use your FA potion/spell/ring FIRST (**)..you try to launch your blade DS... you WASTE your DF
(nothing happens; only FA icon on portrait) AND you loose one point in your available DS numbers left
2. You launch your blade DS FIRST... You use your FA potion/spell/ring ... _then_ you have no problems to use AND the FA effects (both FA+DS icons on portrait;ok), AND the DS, at the same time (DS not wasted). The DS movement lock is not unlocked though (*). Expected behaviour:
1. Even if new dev team thought DS should NOT have the DS 'movement block' unlocked by FA (*)... You should NOT loose a point in your DS available numbers left
; a simple block of the DS launch should be enough (not to loose a point at least)..
2. Well.. if 2. is normal (though the no DS movement lock unlocked is questionable (*) ).. then 1. is not right/logical, at the same time..or DS should be locked/removed in both cases (FA prioritory?..or not).. (similar to speed+FA..must remove the FA item first to get both effects..or waste the speed if FA first..not right/logical too - see also http://forum.baldursgate.com/discussion/26148/bug-free-action-potion-spell-item-speed-potion-spell#latest
, a little the same mechanism /complete waste or not..).
(*)According to http://web.archive.org/web/20121218174907/http://playithardcore.com/pihwiki/index.php?title=Baldur's_Gate:_Classes_and_Kits#Bard_Kits
, the original BG2 clearly allowed the FA effect to unlock the DS lock.. ; "Defensive Spin (...) does only last 24 seconds and keeps you in stuck in place, so a blade cannot REPLACE a fighter or cleric tank... UNLESS they are under the effect of Free Action". That previously allowed interraction effect was removed only with the EEs apparently.
There are no similar interactions problems between DS and speed spells; all working perfectly together, there; you can launch either one or the other first, you will always have both effects together (DS+speed/+ATT), but with of course the movement blocked by DS..and both icons at the same time. np here, perfect..
Nota2 (edit) (**):
Of course, the fun part is epecially with the Free Action (FA) potions : those ones are lasting for 2 hours.. you drink one.. means you are loosing ALL Defensive Spins (DS) for 2 hours too (at least the effects are shorter with spells and of course the simple ring removable at will).. in the current state of the EEs patches; 2 full hours / forced case 1. (all DS will be impossible AND wasted). ^