I'm against buffing Siegfried.
I remember one match, on Amazonas Delta, I was randomly selected as Last Bastion with Euro Alliance as my opponent.
I figured the only way to properly counter Siegfried as Last Bastion would be by stunning Siegfried with giantsbanes.
Uragan?
Maybe instead of a Gap Generator, it could be an upgradable Generator Tower that you first have to build, then upgrade it with an attachment that grants different effects, the Gap Attachment would give your regular gap tower, a Chrono Attachment would provide a chrono field to use the chronolift (maybe provide instant warp for warper units, no cooldown, if possible). And then maybe a third attachment with a third kind of effect, similar to the Iron Guard, just works with defense structures. (I'm totally not considering balance, btw.)
Or just give the chronolift field to the gap generator. :V
I don't like that it's complete useless without the upgrade. :\