Cure the problem not the symptom
I think Dorsi that the problem you are seeing, is not huge empty tribes, but a low player population. Take my tribe for instance. We have maintained active members for over 3 1/2 years and have been active members of the global community be it a small community.
Granted much of the time we have been down to a skeletal crew but usually no less than 3 or 4 active, and as much as 15 at any time. This is not from lack of effort on our part. When the FTP came out we worked hard at recruiting only to have most players waste hours (or days) of our time teaching them the ropes only to have them disappear without a word. Eventually we stopped actively recruiting and relied on serious players to come to us.
Now that the FTP is gone we are going to start recruiting again because we have learned that people who buy the game tend to take it more serious and stay much longer. In fact we should be publishing our next recruitment page any day (still finishing up the details) ;)
As for the resource option, I too am not apposed to this idea however like Wastelandstoic stated, the timing needs to be right. If the population merits it, then I'm in. But with the low population it would only punish those of us who have supported this game for the past 4 years.