Happy Birthday,
The world of Rotax is certainly economic and despite rumours to the contrary the 912 is perfectly capable of being rebuilt at home with the same skillset as any Cont/Lyc. The cost of parts might be an issue but the world is a big one for sourcing.
A group is certainly the way forward and a slightly faster kit build should be possible.
The Jodel etc options do need to be checked very thoroughly for wear and tear.
Best wishes