With (very) few exceptions*, it's not really possible to make a plugin that's compatible with all the different versions. The main reason is that the changes in Adapt v5 to the HTML/CSS were so extensive.
You could make an Adapt v3/4 compatible release (or releases) then do a v5 compatible release.
If you want to include proper accessibility support then you'll probably need different releases for v3 and v4 compatibility as accessibility support changed quite dramatically in v4. I'd be tempted to only include accessibility support for v4+ anyway as it's so much better (and easier to implement).
I don't suggest you support FW v2 - we don't actively maintain this any more. It was really only kept for those people who still wanted to support IE8/9/10 - hopefully no-one needs to do that any more! - and a few users of the authoring tool who couldn't upgrade their framework version for whatever reason.