I keep coming back to this and couldn't decide what it is about it that doesn't seem right, and although I am super lazy to make a unit split it is actually something else... something isn't right...

and now I realize what it is.
These units are the same.
This is like 8 tiers of the same unit, when instead it could be a refined soulkeeper plus something entirely new.

To make this a more reasonable thing to say, look at lilith vs. soulflare, and imagine soulflare was instead just lilith without diagonal charm.

Better phrasing: imagine soulflare was actively updated into a mini-lilith without diagonal charm, removing current soulflare entirely. I think that's the problem here - by adding a new soulkeeper unit which is basically the same, it preemptively erases whatever diversity that could have been added in its place, such as soulkeeperflare or w/e, lol.

for this reason, I think the idea of a unit split is very likely to be incompatible with units that have some semi-unique movetype/effect, unless the divide between the two is so wide as to make one look like a minion compared to the other, or some 'twist' is added onto the new one to split their identities apart from each other along with the moveset itself.