No worries, local multiplayer can a big performance hit, if nothing else. But I’d gladly vote for it – nothing quite like competitive gaming on the couch with family/friends…
Regarding art direction, I think the current look is great! I just think it’s pretty cool being able to get that retro pixel/dither look with a simple (and currently inexpensive/free, though not sure what it’ll cost when the dev releases the newer version on the marketplace) plug & play postprocess effect. If you’re a fan of that “look” at all, give it a try just for your own internal entertainment, I think it deserves more attention 
Regardless, looking forward to trying this when it’s done!