I already made a long post about the Gas Jockey Item Set not really being all that powerful therefore harmless to add as a full time revert but I think some of the other reverts should be looked at to shake up the meta.
Cow Mangler - Given the most used Rocket Launchers (Air Strike and Beggars) can ...

In Defense of the Gas Jockey's Item Set Revert
Section 1.1
By all regards the diversity in Pyro's kit is lacking, not in the aspects of primary Flamethrower for which all are of great use, it is however in the combination of melee and primary that lacks in viable alternatives. There is no doubt ...