I've recently started to become interested in the exchange Queen's Gambit Declined (QGD) from the white side:
[fen ""] 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.cxd5 exd5 5.Bg5
Thematically speaking it's very enjoyable to play. The problem I'm noticing in constructing my repertoire is that black has a couple of move-order tricks up his sleeve to completely avoid this. For one, there's the Alatortsev Variation (1.d4 d5 2.c4 e6 3.Nc3 Be7), however white still has several interesting lines here after 4.cxd5 exd5 5.Bf4 with some highly dynamic Carlsbad structures. The second move order trick however seems a bit trickier to deal with:
[fen ""] 1.d4 Nf6 2.c4 e6
It seems to me as though this essentially forces white to choose between accepting the possibility of a main line QGD (after 3.Nf3 d5 4.Nc3) or the possibility of a Nimzo-Indian if white tries 3.Nc3 in hopes of achieving the exchange variation:
[fen ""] 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4
While I do have some preparation against the Queen's Indian and Bogo-Indian Defenses, the problem here is that this move order seems to force me to study an entirely new system: either the main line QGD (with its endless amount of theory) or the Nimzo-Indian (also very heavy in terms of theory).
So my question is the following: do advocates of the exchange QGD recommend to book up in main lines of the QGD, to book up in the Nimzo-Indian, or to head in a completely different direction with something like 3.g3 (heading into the Catalan, also a very theoretical opening)? Which of those (and which variations therein) are most likely to have thematically similar play as the QGD exchange?