They don't have any sort of ability to provide power to LHCS so you would either need to procure generator vehicles or refit them with ETH supplies (might be hard to do as there might not be enough space). Without power you don't get lights, AC or anything else on the coaches.
As for the regearing it might be possible but a few thoughts, firstly what impact would this have on reliability? They 60s are designed for 60mph running getting another 40mph out of them could have knock on effects on to the loco, such as extra wear and tear on the engine and more importantly the effect on the traction motors and bogies from sustained running at 100mph. So they will need more intensive maintenance more often (expensive) and could be more prone to failure. Also what effect will this have on acceleration, if it takes them 10 minutes or more to get to 100mph then that's going to make timetabling a nightmare.
