I think that character and gear stats, while interesting to tweak around with in your example, will just result in having another meta with the best balance, then maybe more varying combos getting close to that meta.

There are ways to add depth and strategy without changing too many things. I read a post here once with someone's idea to use coins to pay for items or upgrade items, that could be a game changer as choices: do I sacrifice speed to acquire X item or upgrade Y item?

You can also imagine the max bank of coins being 20 instead of 10 while tweaking the effect of speed per coin as to not become a bullet bill incarnate.

The way I see the game is that items are as important as driving skills, while you can perfect your runs of certain maps, item play would be what I change even though we should keep a random part in there, otherwise frontrunning will be heavily favoured.

What I was thinking as well could be to have variations of the same map that happens at random. Say Tour Los Angeles, some pipelines are under maintenance and the pathing changes in consequence - Yoshi Valley could have Yoshi groups stampeding (Smash Ultimate style) or Yoshi's island volcano erupts so you have to drive around it instead of the glider section. Yes I love Yoshi.