I don't know how you'd get round the dev using his own site to pre-process (already published) data or host a list of "banned versions" with bugs that could corrupt data. You can't really choose to have a different developer on the fly.
Maybe you could let people chose a different host for a published photo, but I think if there were privacy respecting ones that easily allowed that the dev probably would have use those instead?
https://streetcomplete.app/privacy
2/2
@vatlark @Scafir @openstreetmap
The postbox thing is apparently an issue with the presets they use. The presets are from another project so it's considered "blocked".
https://github.com/streetcomplete/StreetComplete/issues/5584