I didn't see any need to change this from GC2, any structure you already built is auto-upgraded. And, the old version (fusion reactor/anti-matter reactor) replaced the old with the new in the build list, rather than giving you a choice. Not sure why you would want to build old-style rather than the latest and greatest, and yes, I understand "an old one is better then none at all", if you see the need to keep that in, at least let it auto upgrade, rather than having to go in and choose each structure to upgrade one by one, it could get very tedious when you have a lot of upgrades to do (hell, it gets tedious for me now, ADHD in a 60+ year old, go figure). Well, the few that are included in this version, anyway.
pek