Freezing could promote condensation and thus ruin the powder from the get-go. It would have to be kept IMMACULATELY dry. Probably not worth the risk, IMHO.
Some developing agents oxidize off more slowly when they are dry and frozen. I keep my glycin and ppd developing agents in the freezer in sealed glass bottles. they do not get openned until they are back up to room temp.
So the move seems reasonable. Make sure that you consider foil sealing if the chems are only packaged in platic packets.
I actually have one of these Uni C41 kits left too.
I switched to the Kodak Flexi-color route.
Wonder how long it will last. I assumed the sealed powder would last awhile also but have had powdered Glycin go bad before so I guess I shouldn't assume