A third option is to keep the T Rex!
It sounds as though you really like it and – I agree – finding a comparable replacement will not be easy because there isn’t anything directly comparable.
Here’s the Good News: So far, there is no legal (EPA or other) requirement that owners of the “affected” vehicles turn them in to be “fixed” or accept the buy-back. Also, so far, they are still perfectly legal to drive, including in areas that have annual Smog Check. The cars will pass the tailpipe tests. They only “cheated” the EPA’s certification tests, which are another matter. Until they pass some new fatwa decreeing that either the “affected” vehicles be fixed or turned in, you could just continue to drive and enjoy yours.
The one caveat is that your VW dealer may pressure you to have the vehicle “fixed” when you bring it in for service. But they cannot force you to agree – and you could always take it to an independent shop for service.
There may be a hit to absorb as far as depreciation, but if your intent was to drive the T Rex for many years, this is an irrelevance – or nearly so. And it is possible – very, in my opinion – that the value of these “affected” cars will actually increase over time, due to their functional desirability and their scarcity.
All that said, if you must turn in the T Rex, the Benz GLS350 BlueTec is probably the next-best thing. The diesel 3.0 six makes pretty tremendous torque (455 ft.-lbs.) and has tremendous highway legs, too (600-plus miles).
The manual GTI could help deaden the pain, too!