All they have to do is take the best variation and build from that.
For example take kung Lao tempest
Give him low hat
Give him the hat trap and recall from hat trick
Give him mk11 zhat.
Complete version of Lao right here.
You can do this for everyone in MKXL. Reptile and kitana would be tricky though.
I do like MK9 Kitana overall other than any other version she got past that game
She used to be a character not hard to get into just like her MK2 and UMK3 versions, where her main goal it's to jump kick ppl into air fan for combos, her normals in mk9 are usually short and the ones with better range are also slow, they are excellent in neutral for whiff punishes and really bad for quick punishes, meaning since she didn't had OH or Low combo starters, you had to rely a lot on whiff punishment and outzone everyone else with air fan, and whiff punish with F21 for launches meterless, or standing 3~fan for anti-airs.
If by any chance someone would got into a big no, her b1,4 ex fan cancel was a huge launcher at cost of a bar, she wasn't as crazy but had that nice balance of easy to get into to master the mechanics of the game, i used to love this about her.
Fast forward to MKX she became bloated, had the best jump in the game, best air normal in the game which was impossible to anti-air with normals, had the best damage in the game, the best pokes in the game, the best zoning in the game, an insane overhead, could flute mid air to stop momentum and force a mistake, and she still had a damage buff special.
like WTF did she needed all that?
The best version is still MK9, the rest imo are bad, specially the MK11 where she was designed around a single string
As for Kung Lao, while i do love Hat Trick and get to surprise ppl whener i play it even today, i understand the variation isn't for everyone, as it was the most creative and i think peak Kung Lao, not many ppl had the chance to experience it.
But by far i would pick MK9 version of most characters except sonya, for base and build from there
For example, i noticed that Perfect Legend which was a renowned KL player, barely could do his MKX fist flurry string, which lets be honest, it required execution but was also equally just as rewarding.
I would pick up on that to give him a variation some strings for example:
1121 just like mk9, same string easy to get into and easy to connect, so ppl like PL could still do combos from it, but with less damage
11(212)4 just like MKX with higher damage, higher launch height, better chip and better utility overall for those that master the string, this way you would bridge that gap in between Kungs
MKXL teleport options over MK9s and all others
Also, hit hat overhead it's iconic at this point and i can't see KL without it, but i do like his new B2,4 being a higher damaging one since he can't hit confirm it
What i hate though, it's a move that was always d4 in the air (dive kick) now form some weird reason they made it db4, i don't understand why they have to change things all of the sudden, pretty sure no Lao players asked for this weird change.
Some designs were already peaked and i don't see them overcome it
Skarlet in MK9 it's greater than anything they did prior to that, specially the shitty MK11 version of one string and shitty strings
MK9 Kabal was vastly superior in design compared to MK11 where his traits were no gab, and then they had Air Kabal
Trapping Sub-Zero with Ice Clone, Ice Puddle and Ice Shower over anything it came after, NRS hates trapping currently, which was a very effective style against players who like to mix at 90% of the time