Yep, maybe resampling ANA 1.5 factory presets could have been a workaround solution, that said, it won't give us the same amount of control than with original presets. For the source sounds, it's again a compatibility issue, ANA 1.5 was using .PCM files where ANA 2 is now using the .WAV format. PCM audio files aren't easily editable for conversion since not many audio editors can open that file format, and still, even if you manage to convert those source sounds into WAV format, the preset design has then to be done again anyway.
So in the end , there's no easy & reliable solution and we're left with having to re engineer those sounds & presets ourselves like you mentioned. Don't get me wrong, I perfectly understand the hassle for ANA 1.5 users, but at some point, I do think we have to accept that it's now a discontinued product and won't be maintained by Sonic Academy, there's also other issues like recent MacOS versions compatibility leading to the Plug-in being broken and not usable anymore. It won't be the 1st manufacturer to drop older product maintenance & availability, those things happen unfortunately.
Now in terms of presets, the incompatibility between ANA 1.5 & ANA 2 might be seen as a wrong move, but I think that we're well covered with ANA 2 factory ones and the huge collection of presets packs released since it's launch + the fact that now using WAV format for samples & being able to drag & drop our own samples onto any Sample OSC in ANA 2 is definitely a huge improvement. There's also some upcoming updates such as Multi-Sampling and brand new sampler OSC features that would hardly have been possible using he PCM format + also MacOS notarization & Big Sur compatibility in development right now. So in the end : let's embrace ANA 2 I think, even if that implies some sound-design work to get back some of our beloved ANA 1.5 patches