If they are ever to allow M&K support on consoles, then using them should restrict users to having cross-play on.
The danger is people turning off cross-play and playing exclusively with console players. M&K is just hands down superior to controller.
Having no aim-assist for controllers is maybe fine in the level playing field of cross-play off. However, for cross-play on, aim assist is needed to try and balance out against M&K users.
Very, very few people can claim they are as good with a controller as they are a M&K, and I would personally argue that in those examples if the individual put more time into M&K they would quickly realise they can do even better.
Obviously the above applies to being on foot. When it comes to flying a helicopter or a jet, things change somewhat.