To be fair: Ice Breaker is probably the worst example you could have used. ^^
If the upgraded exotics really do start over at 302 attack, an unlevelled upgraded Ice Breaker is nearly better than a fully vanilla one. ^^ Its main perk doesn't have to be unlocked.
For all the other ones, though, you are right.
I wonder how armors will work. If they somehow manage to make it so you stay at the same light level when upgrading them, this could work nicely...
Right, that's the point though. I worked a lot, you didn't. You spend 7 Strange Coins and your weapon skips through all my work and goes straight to a higher attack level. Meaning I upgraded it fully just so I could have a better weapon for a few weeks? But now that's meaningless and we have the same thing? It's a slap in the face.