huh? glue/repair a wet system?? what is that mean??? lets start off with assumptions that the work is dont properly and there is no leak... if there, it wont really matter if you ahve a union or not... and depending on where the leak is, it could be really screwed if you have to tear apart a bulkhed or something like that.
the bulkhead system you have seems not for just in case of leak, but rather to take apart when you move or clean or upgrade or something... and if that is the case i still stand behind my suggestion to not use them and just cut the pipe at those union locations and then install unions when you move, or use couplings... by that time, i am guessing it could be years, hopefully...
also, i would put unions and valves just above the closed loop pump, and return pump, so you can just disconnect the pump and pull it out for routine maintenance, prior to failures... and repairs... you will ahve to unscrew the union and pull the pump and a few feet of water filled pipe out to maintain the pump...
not tryin to be a pita, but when you post a best ever thread, you should expect me at least to say something something... hehehehehe
some things are a 50-50 some are a 49-51 and some are a 90-10
also keep in mind that after i finished my perfect plumbing i was nit picking myself...