They have plenty of power IMO. As for bigger tyres, they look cool but they’ll likely mean less overtaking IMO – what happens when it rains? You have less mechanical grip and get better racing…
I think you have that arse about face! When it’s wet their aero doesn’t work anywhere near as well (partly because wet/inters raise the ride height), so it levels out the field.
BTW They’ve tried high downforce/low mechanical already. We ended up with (admittedly cool) cars looking like this:
…and no overtaking due to the dirty air in their wake.
So in 2014, they went the other way. Reduced aero. What happened? Much closer racing down the field.
Bigger tyres would also increase the tow effect on high speed straights and help with overtaking.