I don't think we should feel the need to add optional overrides every time we add a new feature.
From our perspective as maintainers of gaiatest, adding more overrides means more flow paths and more places for potential regressions. Similarly this feature is likely to only be used by a tiny percentage of users, if they even know about it at all and they have the potential to misuse it, too. If someone requests it in the future I'd take it onboard but otherwise it seems like extra work for no immediate gain.

I've looked into the temp folder and it seems we can do it in Python so I'll give it a shot in the next commit.