Setting gamma to 1 (i.e., eliminating gamma from the verification key)

[imeckler]

It might be worth eliminating gamma from the verification key. I guess this isn't a huge deal, but my understanding from talking to @arielgabizon and Mary Maller is that it isn't actually necessary and you can just use the generator of G2.

This is useful from the point of view of proof composition because it makes the verification key smaller.

[arielgabizon]

I'd be slightly hesitant to remove it altogether. You could argue the version with general gamma is potentially more secure as there are less elements the prover can generate in G1 when gamma is unknown, assuming he only has access to the original Groth16 CRS elements.
When you generate the parameters in an mpc at lest the way we did it in Zcash you get these elements anyway so you indeed lose nothing by setting gamma=1.