MFC has a wrapper, CTaskDialog.

This is the first meaningful TaskDialog implementation in Wine that supports more than just plain old Yes/No/Cancel buttons:

https://github.com/wine-mirror/wine/commit/995b6900a7002b716654edbe28ab2ba992433c4c#diff-9e4518b138da0b92fbc6f7a8fd89c981c445f646c212e05571dab2d191fbf451

This would raise the required Wine version to at least 2.5 (2.11 for custom buttons). We appear to have no Wine 2.x users according to update statistics, but a handful of people are still on 1.8.

Requiring Wine 3.0 should be trivial by now, however, we still do have Windows XP builds.

We could still use Vista dialogs and fallback to even worse UX for Windows XP: "click Yes for $ACTION, click No for $OTHERACTION".

For those messages currently supported by the Reporting namespace, that would work, yes (and if the prompt is worded properly, the same prompt can be used for both dialogs without any additions). However, this wouldn't work for other dialogs - I particularly wanted to replace the MsgBoxHidable implementation. But since this only affects XP, I guess we could simply assume that the user was going to hide the message box (which is the default action anyway) for a fallback.

That would be OK, I think. RETRO builds can have reduced functionality.

Technically only Reporting::Confirm and Reporting::RetryCancel need to be ported. I suppose the API could pretty much stay the same, with the only difference that labels for the different actions would have to be provided as additional arguments to those functions. This would make it very easy to keep the dialogs usable as messageboxes as well.