This is a really good point to emphasize. If the statement from the developers is that these affixes are difficult to change after implementation, that makes it all the more important to get them right the first time. They should be taking the difficulty of changing them after the fact into consideration in the design (or re-design) process.
That also means that if they’re going to go through the process of ‘tearing the house down’ to change some like Doomed Blade and Doomed Club, they should really fix all of those similar problems at once so as not to have any reason to go through that rebuild a second time.
I would suggest scrubbing all weapons to correct any violations of these two basic rules:
For weapons that create or convert gems, the affixes should only ever create more gems of the same color, or destroy different types of gems. That seems very simple and I think the vast majority of players would agree with that because it removes the counterproductive aspects.