I was actually fine with the old school counterattack posts. I'm also fine with the new mechanic, although it's a little annoying to have to periodically go in and clear warp relays. On the other hand, it's usually a great excuse to take my fleet ball and zap a bunch of free-floating AI guys - which I don't do often enough, so they often pile up and take out my un/poorly defended outlying worlds. The part where stuff can warp in wherever it pleases is ok - I play on 'realistic' maps, so carving out a chunk of the map where I have real "outer" and "inner" worlds usually costs more AI progress than it's worth. My territory usually looks like a convoluted snake with "dots" here and there.
I do like Toranth's and winge's idea 1b, sending actual *threat* on waves. Load up the warp relay like a transport or a carrier, then, a couple of minutes to "spool up the drives". Meanwhile, the player gets an alert and has the two minutes or whatever to "do unto others before they do unto you". If you ignore it, BAM, right in the rear echelon.