A usertext field would most certainly be useful for many things. Very useful.
Problem here is that it would not solve the problem of “remembering” part/assemblies of different kinds (like Polysurfaces, Blocks nor Groups, same conceptual problem applies for all of them). As soon as you explode any of those, the irreversable happens - the parent is lost, and thus it’s joined name, One can no longer answer the question which of the exploded parts or splinters should be considered the “parent”? (if one would like to re-join the parts/splinters again).
For this reason I imagine that you could not get away with anything less than creating an extra “ghost parent”, or “pseudo parent” as I called it, before exploding Polysurfaces, Blocks or Groups, and set all the parts / splinters to point at that “ghost parent” as a last step in the Explode command. Then it would be possible to reconstruct any exploded parts/splinters back to it’s former “joined name”, provided that they are not joined into some other constellation (then the “ghost parent” would change on next explode, aso).
But a usertext field would really be useful for many dirty tricks by scripters. A field of unlimited size at that. 
// Rolf