It is likely that travel between EU countries will no longer need special permissions.
It is possible that IFR may be permitted in pernit a/c. It is being talked about anyway.
The special permissions are already a non problem. The problem with building an aircraft now and expecting it to be IFR later is huge. We have no idea what the new rules will be. One possible scenario is you will have to build an exact duplicate of a factory approved machine to get the VFR restriction limited. Another is it would be assessed against a set of currently unknown criteria. If I was building my MCR now I would go for a full uncertified Glass panel, but I expect this would stop any chance of removing the restriction.
RV7 v RV9
When I was looking 5 6 years ago I put the RV9 on the short list because you can use quite small engines with low fuel burn. In the end the considerable savings offered in running costs by the Rotax won the day. With the price of Avgas likely to hit £2 soon and £3 in the not too distant I would be very nervous of anything burning more than 15 20 lph, or something which could not be run on Mogas. Despite my MCR only burning 15lph of Mogas, fuel is still my largest single cost
Rod1