I believe I would agree that there needs to be or could be another factor that can influence/temper/control what comes through a Gate and when. Objective points/flags that do such have potential. I think right now you could argue that there is a race to get Catapultasauri on the field, since they can deliver tremendous damge in short order to anything. Shaking that race up a bit strikes me as a good idea.
On the other hand, would that be detrimental to the idea of fast victories?
I think this idea is kind of silly. Flags are supposed to be bonuses. You are supposed to capture them. It wouldn't be fun for your demigod to "capture" negative curse flags for just walking past them.
I maybe should have said earlier that I like the idea of negative flags in general, but not the idea of deliberately making them incidental captures. Since War Score was implemented, *all* flags are inherently bonuses: what I think is interesting is the idea of combining that bonus with a negative (so you need to decide whether the trade-off is worth it; obviously this only is interesting if the answer is sometimes "yes" and sometimes "no"). However:
It would also make it easier for a stupid or malicious player to grief his teammates.
Ew, I didn't think about that (partly because I rarely play online games). That seems to me like a good reason not to do this.