I still think we may not end up getting a full character with timed hits, maybe only some moves like Smashes instead. I know people want him to have it because "it would accurately portray Mario RPG"; but in general I think timed hits are super tricky to execute properly in a fast paced game like Smash. Sure there are already characters with "timing" mechanics, but usually that is a small part of their kit. That combined with the bad netcode online and the buffer system, would make it pretty annoying to use a character that largely relies on timed hits, especially if the timing is narrow. They could broaden the timing window, but then it they would have to reduce the "power" of timed hits to compensate for it being easy to execute.
Another "wackier" idea I had is if they made Geno a more positioning oriented character. I think Geno would primarily be a character that has a good range, but they can make it so that most of his attacks have sweetspots at certain ranges, differing for each move. If you hit outside of that moves sweetspot, you wouldn't do a whole lot of damage, but if you hit that sweet spot you'd do a whole lot more. Think like Marth, but different ranges for tipper for each attack.
So for example these could be the sweet spots of certain moves:
Geno Whirl: Likely a very fast projectile, that travels a long distance. The spot should be around the end of the move, where it would deal massive damage; however, hitting near the start or the middle wouldn't deal a lot.
Geno Flash: Another projectile with a long range. This one would travel at a slow/medium speed but would likely have a larger hitbox compared to Geno Flash. However, unlike Flash the sweetspot could be around the middle of it's total range rather than at the very end.
Geno Beam: For beam, the sweetspot could be near the base of the attack with the damage dropping off the further away you get from it.
They could also use this as an excuse to make Geno an extremely fast character too. As you would need to rapidly be able to reposition yourself so that you are able to hit your sweetspots. So one second you'd be zoning with the likes of Geno Whirl, and then switching over to approaching and trying to land the Geno Beam up close.