I wonder if Vans might consider at least designing the possibility of using a non- Lycoming engine. If they are doing a 4 seater high wing the UL Power 520 T seems like a interesting option. It provides the same sort of sea level performance as the IO-390 but you are still getting close to 220 HP at 15,000 ft.
It also has the advantage of being about 40lbs lighter and FADEC controlled and uses mogas. The problem is it doesn’t have the pedigree of a Lycoming. However for those who want a reasonably quick 4 seater high wing it sounds like a decent option.