Hmmm – I think there’s a number of ways you could do it, just not sure you’d want to. And it’d be a bit of a bodge.
Most fixed hubs are 120mm so you’d be squeezing the drops together when tightening the wheel. You can buy 135mm ones from Surly, I’ve not seen any 130mm ones but thats not to say they don’t exist.
Second (and perhaps most important) consideration is chain tension (as you mentioned). On a standard drop-out with normal BB, you’d need to either use a chain tensioner (or a knackered mech) or find the magic ratio. The first would be a proper risk – ok for SS’ing but I wouldn’t want to put that much strain through one riding fixed and the second limits your choice of gearing which is quite important!
You’ve got other stuff like chain line to consider as well. I’d be more inclined to buy a cheaper fixed frame or bike if its something he really wants to do. You can pick up second hand stuff on LFGSS or new from Mango or one of the many places doing cheapy fixed bikes. Plenty of Langsters and Cinelli’s about
Of all the things to try to bodge, fixed isn’t one of them. If it lets go which from the above solutions it probably will, you’ll be picking your teeth off the floor or trying to cut bit of frame out your knackers. Mind you, if you want to slow him down…