I don’t see the ultra-light weight motor glider electric power as very likely – the weight of batteries demands strong and hence heavy wings.
I think the Arcus approach – batteries spread along the wings to minimise bending moment at the root – as the optimum concept. Retrofits like my FES, with all the added weight in the non-lifting fuselage, are less optimum (but all that was available to me).
As always, battery capacity (absolute, and per unit weight) is the limiting factor, but getting better over time. There is also a fire risk factor from batteries, but then there is too with internal combustion engines and, perhaps, with small gas turbines.
Chris N