I think it will be difficult. The reason why KARD hasn't disbanded yet is because of their chemistry with another and only being 4 members.
I can see it getting difficult if there are gonna be more than 6 members for a co-ed group and keeping a nice atmosphere with each other.
And especially for younger co-ed groups it will most likely be really awkward.
KARD has tried it and succeeded and also failed at creating choreos that fit both. While sometimes more sexy and on the lewd side, they also have a bunch of non-sexy and lewd choreo parts.
It's difficult balancing the different heights and bodies each member will have. K-Pop is obsessed with synchronization so it could lead to a lot of backlash if a co-ed group isn't that.