I would like it if there were less restrictions in accessing areas.
I'd like them to impose risks to the player.
Someone already brought up this idea before about getting lost on a route with high-leveled Pokemon and skilled trainers while you are just on your Lv. 10's. This should be enough to point you back and find a different route without obviously saying that you're not supposed to be there yet. If you managed to get through and reached a town/city, then that would quite an accomplishment. Although pretty sure they will still restrict you on going further.
Also, it would be cool to have alternate routes in reaching areas again. Fuchsia for example.
You have three options: (a) Celadon west exit to Cycling Road; (b) Lavender south exit to Routes 12-14; or (c) Vermilion east exit to Route 11, then south via Routes 12-14 again.
They did the same with reaching Humilau City where you can either choose to go via the Marine Tube or pass by the sea routes on the east, but the other being just a bridge with no challenge at all.