not sure,i was wondering this myself i geuss it might be possible if you add to those lines in the gameplay constants file

I have not tried what you are saying but I am re organizing my research. 

The is only so many positions to place the research

researchWindowLocation
 block 0
     pos [ 7 , 3 ]   <---- 7 is the last row
     ResearchField "Diplomacy"
 Prerequisites
 NumResearchPrerequisites 1
     ResearchPrerequisite
         Subject "RESEARCHSUBJECT_PACTUNLOCK_STRIKECRAFT"
         Level 1

Try to make a ResearchPrerequisite thats in row 7 and put the new one under. Still 8 labs but needs more research. like the planet cannon.

fredled is right; I'm wanting research to require more labs. We'd essentially create a new window after diplomacy specifically for this research. I'm not wanting to go further right on the screen, but instead require more labs than 8. I mean, after you conquer three to four planets, you have all your labs, and then just que up all your research and wait for it to finish, and then go kick everyone else off the block. We're aiming at making research late in the game viable by requiring numerous labs.

I'll have to look into that. I looked at the file, and I'm betting you're right that tiers can't be added. At least that gives me a little something I can play with if I wanted to. Thanks for the assistance guys!