The sword of doom doesn't use anim OB\11 from a look at it's ab sequence, in fact I copied this exact sequence to replace your Zack normal attack, and the high jump effect part is likely produced by the use of the opcode D0 there.
It must be the quadra-cut that use anim 11 but I didn't need to look at this sequence.
So, well, I think it's the best I am able with this customization for now:
https://ufile.io/mphwyrlgBlade beam and meteorain are probably uninspired but they do the job, and I think Braver, cross-slash, climhazard and finishing touch aren't too bad at all, like this Zack, he isn't so bad at all at the end.
Err, I gave up on Omnislash for the current state of the model, I just can't see any way to produce anything that remotely fit the setup needs of the real Omnislash with the animations currently integrated and the lack of space in the ab file. Some new animations, at least one where this Zack make a equivalent number of slashs in 46 frames would be the best, and maybe the only way to have him perform this limit, well I will think about it but right now I don't see a alternative.
I still replaced the animations, maybe it will "work" to at least not bug the fight, and maybe it won't, didn't even want to try this one in game.
Fortunately, you don't have to use limit level 4 so...
Maybe if I decide to have a Zack fight of sort in my mod, I will make animations that could fit, but so far I am undecided on this. But if I decide it later, this repurposed 1st SOLDIER would definitely be a very good base for sure.
Well, in case it could help someone, my 'map' recent notes on the ab file of Cloud: (The real unmodified Cloud)
From offset 190h, after the 'header' section
00 FE C0: IDLE (00)
01 FE C0: WOUNDED IDLE (01)
10 FE C0: Some damaged pose, paralysis status maybe?
E5 06 F1: KO
B3 F9 03 ED E3 EE: Jump forward, change command (for under small status I think)
B2 F9 03 B1 03 B1 E3 EE: Jump forward, change command
B3 F9 04 E4 E3 EE: Jump backward, change command (for under small status I think)
B2 F9 04 B0 04 B0 E3 EE: Jump backward, change command
0F F2 E5 EE: damaged\regular hit taken
10 11 F2 E5 EE: damaged pose 16 (paralysis?) then go back to idle with 17
12 F2 E5 EE: damaged, like when taking a hand grenade for instance
05 E5 EE: Dodge, Evade anim
AB 90 01 00 00 08 F4 0F F3 FA E5 A6 EE: Cover
13 E5 EE: enemy skill learned
18 19 E5 EE: A other dodge? Not sure when these moves are done?
B4 02 F1: victory pose
95 07 FE C0: Escape
C4 90 01 06 07 FE C0: Escape vanishing I think
04 FA E5 EE: jumb backward again?, is it used?
E7 00 F1: No idea what this is for, the 00 is a byte, not a anim call
E5 C4 90 01 06 12 E7 00 F1: A other call to damaged anim 18 but that one should make the character move position while it happen
E8 FC 03 ED E6 EA 0C 0D EC 0E 04 FA E5 EE: magic cast
E8 FC 03 ED A4 EA 0C 0D EC 0E 04 FA E5 EE: E.skill cast
E8 FC 03 ED A5 EA 0C 0D EC F4 0F F3 0E 04 FA E5 EE: Summon cast
E8 FC 03 ED D8 06 15 00 09 EA EB F4 0A F3 04 FA E5 EE: throw curative item
E8 FC 03 ED D8 06 15 00 0A EA EB F4 0A F3 04 FA E5 EE: throw damaging item
FC F0 D8 00 1A 00 1A D1 B0 04 00 00 04 F0 1B F7 01 1E 1C FA F0 1D E5 EE: attack
FC 03 ED F7 10 1F 04 FA E5 EE: slash all\flash
FC F0 D8 00 1A 00 1A D1 B0 04 00 00 04 F0 1B F7 01 D8 01 D6 02 16 F4 06 F3 26 FA F0 1D E5 EE: Steal?
FC F0 D8 00 1A 00 1A D1 B0 04 00 00 04 F0 1B F7 10 21 28 FA F0 1D E5 EE: D.blow
FC F0 D8 00 1A 00 1A D1 B0 04 00 00 04 F0 1B F7 10 20 27 FA F0 1D E5 EE: morph? second level?
FC 03 ED F7 01 20 04 FA E5 EE: morph? first level?
FC 03 ED F7 01 14 F4 3C F3 04 FA E5 EE: sense
FC 03 ED F7 01 14 F4 5A F3 04 FA E5 EE: sense, which one is used? Both?
FC 03 ED F7 13 15 04 FA E5 EE: manipulation
FC F0 D8 00 1A 00 1A D1 B0 04 00 00 04 F0 1B F7 01 1E 9E 00 F7 01 22 23 FA F0 1D E5 EE: 2X cut
FC F0 D8 00 1A 00 1A CC 04 CB FF E8 03 FE FE 00 08 08 F0 1B 1E F7 03 F4 06 F3 1C FA F0 1D E5 EE: Mug?
FC F0 D8 00 1A 00 1A D1 B0 04 00 00 04 F0 1B F7 01 1E 9E 00 E5 BD B0 04 00 00 F0 F7 03 22 9E 00 E5 BD B0 04 00 00 F0 F7 03 24 9E 00 E5 BD B0 04 00 00 F0 F7 03 29 1C FA F0 1D E5 EE: 4X cut
E8 FC 00 E0 EA F4 19 F3 EC F0 D8 00 1A 00 2C D1 B0 04 00 00 04 F0 2D D8 06 30 00 2E FA F0 2F E5 EE: Braver limit. Limits note:I don't know how the game sort it out, probably through the exe, but here it consider that anim 00 01 02 and 03 from blaver.a00 are anims 44 45 46 and 47...
E8 FC 00 E0 EA F4 19 F3 EC F0 D8 00 1A 00 2C D1 B0 04 00 00 04 F0 2D 2E FA F0 2F E5 EE: Cross slash limit
E8 FC 00 E0 EA F4 19 F3 EC 2C 9E 00 EC 2D E5 EE: Blade beam limit
E8 FC 00 E0 EA F4 19 F3 EC F0 2C D8 00 1A 00 FB 40 06 00 00 F0 2D D8 19 30 00 A8 26 08 2E FA F0 E5 EE: climhazard
E8 FC 00 E0 EA F4 19 F3 EC 2C E5 EE: meteor strike
E8 FC 00 E0 EA F4 19 F3 EC 2C E5 EE EC E5 EE 00: finishing touch
E8 FC 00 E0 EA F4 19 F3 EC 2C 2D 2D 2E FA E5 EE: omnislash