Hi Shianne,
We've been tweaking a Tank Priority loot system within out DKP for a while now. What we are currently allowing is that items on the tanks precreated lists that are specifically for tanking are granted FREE (0 DKP) with a Tank Priority bid. Only our core raid team tanks are able to use TP. The tanks we have will not be abusing the system and the bulk of our raiders understand the importance of having geared up tanks, so this isn't a really big deal.
Hope this helps a little bit.
This is actually very similar to what my guild did when we were a raiding guild. Because most people simply cared about heavy damage for pvp, we would charge less for progression items like resistance gear and tank stuff, since no one wanted to spend a lot on them anyway.
Then again, EQ2 likely has a different dynamic than WoW, but you can always stipulate in the rules that the officers can override the DKP with regard to tank-specific items.