Yes, Argent77's function is faster than the one I wrote. So I included it into my process and use it with arrays corresponding to the animation formats. But I need to check every range of index and every step.
ACTION_DEFINE_ASSOCIATIVE_ARRAY GW_slots_BG2EE BEGIN
// FORMAT SLOT_MIN MAX => SERIE
// ------------------------------------------------------------------------
BG1ML4, 0x1100, 0xff => ML41 // BG1 MONSTER LONG 4 PARTS
BG2SP4, 0x1300, 0xff => SP41 // BG2 SPLIT 4 PARTS
DRAGON, 0x1210, 8 => DGN1 // DRAGONS (9 PARTS)
BG1SML, 0x7110, 2 => 1SML7110 // BG1 MONSTER LONG (LARGE)
BG1SML, 0x7120, 2 => 1SML7120
BG1SML, 0x7130, 2 => 1SML7130
BG1SM, 0x7210, 4 => 1SM7210 // BG1 SIMPLE MONSTER
BG1SM, 0x7220, 4 => 1SM7220
...
BG1SM, 0x7610, 6 => 1SM7610
BG1SM, 0x7410, 3 => 1SM7410
BG1SMA, 0x7d10, 8 => 1SMA // BG1 SIMPLE MONSTER (ANIMALS)
BG2SP, 0x7300, 0xff => 2SP1 // BG2 SPLIT
BG2SP, 0x7f00, 0xff => 2SP2
BG2UN, 0x73f0, 0xff => 2UNSP // BG2 UNSPLIT
BG1ML, 0xa200, 0xff => 1ML // BG1 MONSTER LONG
SPEC, 0xd000, 0xfff => SPE // BG1 SIMPLE MONSTER (RANDOMLY FLYING CREATURES)
...
END
As you can see, I can add the new slots 0x7111 and 0x7112, but need to jump to 0x7121 for the next one because 0x7113 to 0x7120 don't work.
Moreover, the dragon format seems to be buggy (confirmed by Avenger) and needs to be fixed before I can add new dragons animation slot . It is a shame I can "play" with my tarasques in BG2+IA and not with EE.
I am still checking all the available slots.
Speaking about porting IA to EE, it is not very difficult. I already ported about 50s of them through my mod. It just needs a workaround so that WeiDU can handle special characters (Ø, Þ, µ...) and change them before copying them into EE override folder (i.e. µBO becomes IABO if it is an IA animation file or GWBO if it belongs to my mod) and writing it into the animation ini file.
When my checking will be over, I could have a look to the IA tp2 file and try to make it compatible with EE.