i agree with skipping the co. car....
if the car is paid off, and isn't costing you a monthly, make it pay you back!!! why not? i mean, if you wanted to keep it pristine, in the garage, and just put tiny miles on it, and keep it forever, mod the hell out of it, etc. then maybe it wouldn't be right for the long hauls, but otherwise, i think it would work our pretty well.....
i would not, however, buy my zo6 (or whatever) on the money i was making off the ms3. i'd probably set myself up a little cu account, and put the earnings from the car there..... for use in repairs, maint., and tires, etc. and just ride it out... as soon as the 2 years were up, or the car started giving me any reason to not trust it out on the road..... then there you are...
if you kept it together, and treated it well, then you could have a good bit of cash, as a down payment, and you could either keep the ms3, or let it go.... miles or not, these things will always have a value, i bet.
hell, i'd do it. the ms3 is a hoot of a road car, and pretty versatile. don't think of it as 'putting miles on my baby'... think of it as 'my baby paying me back for being so good to her when i was paying that note'