Improved + low recoil - the 105mm on the AMX-10RC as it is can't exactly fire legacy 105mm APFSDS rounds.
Replace the hydraulic traverse with an electric drive, add some sort of modular armour option (it's really a good idea when you have this vehicle that's meant to be used for everything between low-intensity peacekeeping and rapid flank attacks in Fulda Gap scenarios) - maybe even replace the aluminium alloys used in the body, which I'm sure you can find a contemporary alternative for.
One of my biggest issues with the AMX-10RC is the ammunition storage and the cramped four man crew in a vehicle of that size. If you can take all the electronics out of the back of the turret, extend the bustle somewhat, move the commander to the foward left of the vehicle, add some sort of bustle autoloader and move the electronics to where the loader formerly was, that might be the way forward for a modern reconfiguration of the vehicle. Though if you're going to take it that far, I suppose you might as well replace it altogether.