There's more to rebuilding hydraulic parts than meets the eye. I have a longstanding grudge match going on the Saab bulletin board on the subject. My adversary believes one never should use remanufactured parts, but I believe the pros have equipment and resources unavailable to the home mechanic.
Granted, reman quality can be hit or miss, but home rebuilds are, in my opinion, almost always a miss. Here's why:
Got scored pistons or bores? You probably do. Those nice $2 seal kits aren't going to last in that scenario. Got a cracked housing? You very well might, but you can't know without expensive equipment and proper training.
I may be giving remanufacturers more credit than they're due but home rebuilding gives me the creeps, particularly for safety items like the brake systems. The pro-rebuilding argument I usually hear goes something like, "I've been doing this on all my cars since 1928...." But this is not a '68 Malibu, and there's a lot downstream of this part that depends on some pretty tight tolerances.
No idea what the cost or availability of remanufactured MKV calipers is of course, so I may be leading you down a primrose path. But if the caliper costs anything like $100 or less, I'd spend the dough on a new or reman part myself.