Instinct, the idea is that if you're going to be "mass producing" the build item on multiple planets, you'll want to research it, because not doing so will cause building to take longer per item. Granted, not as long as building and researching combined, but if you're building it over and over again, it will add up, and it will be considerably longer than just researching it ahead of time.
PJ/Tarnus, I can understand your position on reasearch and building only staying on one planet, and what I'm arguing is mostly for the sake of realism rather than balance in the game, though I still think my idea would add a little bit of strategy. However, it's not important, so do whatever.
Here's just something I'd like to point out. Unless the player wants to be building lots of different things, or researching a lot of different stuff at the same time, I think they're just going to upgrade one planet so high it's nearly impossible to take (since planets get a boost in tech levels, and they are way cheaper, this is quite possible, just pointless at present) and then do all their research on that planet, so they don't lose it. Or, if they do want to be doing multiple researches at the same time, they could still just do that for multiple planets. I'm not saying this is a bad thing, but it is something that seems likely to happen, so I'm just pointing it out.
And since these planets aren't going to be producing credits (they're population is on research and build, not credits), they may even keep these planets in a seperate branch of SG or another SG all together. Or, maybe they'll use their gate planets for research and build. That's probably what I'd do. That's already the most protected place in the SG, and gate planets don't really need to be money makers. Also, by upgrading so much, they may help prevent loss of valuable SD techs.