I think the reason Kumatora wasn't referenced as an alternative color for Lucas was simply because she's a girl and Lucas is a boy. Robin's alternative colors for both genders only reference other characters that share their gender with them, for instance.
Edit: the closest exception is Captain Falcon's pink alternative color, referencing Jody Summer. To my knowledge he's the only one referencing someone with the opposite gender however.
On the topic of Mother, it bothers me whenever people say the series is "dead." The word I use is "finished." This is because despite how there will no longer be any sequels the fanbase is still alive and celebrating the series constantly, and as a part of that fanbase I can reassure you it's out of genuine love and not some sort of desperate wishes for continuation of the series. The closest equivalent to that is asking Nintendo (nicely, believe it or not) to please release the remaining Mother games worldwide. And we think it's working too, with EarthBound Beginnings finally coming out recently. Patience and a mature, professional attitude really pays off.
#NintenOrPorkyForSmashEvenIfItMayNeverHappenLol