@popey - please see the (updated) auto-connection request considerations and the section under it on manual connection mitigations. Snap publishers are in a position to do reasonable UX to guide the user on how to connect interfaces. I agree that snapd could make this easier for publishers and users, but we shouldn’t wait for “magic”-- if you have identified this as a “frustrating gap” (which I believe you are right to call it that), please raise this via snapd’s stakeholder process so the work can be prioritized accordingly (I suggest this conversation happen outside of the forum between you, @mvo, @pedronis and @Wimpress).
As store reviewers, we are in the difficult position of trying to provide both a curated store and a good publisher experience, but our voting process necessarily must make compromises at times. In this case, we have voted consistently in favor of maintaining the user’s voice (see aforementioned URL) for removable-media, even among similar requests for other browsers. I don’t see opera’s request as different from those. Considering that opera can choose to perform the items in the aforementioned page until such time that an even better experience is available, -1 for auto-connecting removable-media.