There is so much on this forum about brake upgrades that it isn't really worth re-hashing it all. Marco is a guru when it comes to the options. Look for his stuff.
I've got a VT upgrade on the front with the standard size 296mm rotors which actually fit under my 15" CSA rims. I think you MAY be able to fit the larger VT-VY rotors (330mm?) under 16" rims but not 100% sure. I fitted the VT master and booster with the front upgrade all at the same time. Modified bracket needed to fit the VT booster which you can do yourself or buy from Marco. I prepped the bracket myself using Marco's specs and had it welded by a local engineer cos I'm a novice welder and you don't want it to fail down the track.
The result is a huge improvement on the standard brakes. I've still got standard brakes on the rear. If you go bigger on the front it might become more desirable to upgrade the rears as well just to keep things in balance.