I would also prefer the format proposed by Greg, with a minor tweak of having the units after the value. so
mass = 1.0 [kg]
I don't even mind the * sign, or even the u. (since those would be easy to replace afterwards). So something like:
mass = 1.0 * [u.kg]
It would also be nice to drop the ^1, since that is the standard power and isn't really needed.