Feel free to correct me if my information is wrong but from what I understand, there's only two ways to get a combo base:
From breeding the required coats, like ebony&ivory, Albino&korat, chartruex, Maltese, or any of the Egyptian bases.
You can also apparently get it from breeding the combo to a required coat, like Gilded&Anubis or Soul&Ebony.

I'm proposing a slight change. Nothing that would undermine it too much, I love these bases being rare as possible, and I actually don't mind if this doesn't go through, but i am suggesting a possible change to mechanics.

1. Making it possible to pass a combo base if you bred a combo base. There would be some restrictions (pulsar & pulsar were made to be only passable in July, the rest of the time you can only pass them to each other, I think that should remain, and cloudburst being weather restricted to pass) but if you had like a nadir or something similar, you would be able to pass it from a random breeding, it would just be even more unlikely then if you bred it to one of the coat requirements.

2. This is the suggestion I actually like, being passable but ONLY To a lion with identical coat genetics. For example a soul&ashen would NOT be able to pass a soul base, but a Soul&chartruex pairing could. It would still be much less likely but possible. And again I think pulsar and cloudburst should keep restrictions, and any other combo that is super specific that comes out could be too.
to clarify, with this one, the combo base would still be inheritable to its core bases and to the bases sharing its exact genes.

So, comments, questions, critiques welcome, like i said I actually don't mind if this doesn't go through , I just think it'd be nice to be able to broaden horizons a little bit with breeding combo bases, It just seems kinda restrictive, but i don't mind em being rare, I love it. So let me know what you guys think