Will be possible sometime in the future to play Frisian Draughts from costum position? It would be great to practice difficult middlegames and endgames. We can already do it for Draughts-64 and standard, so why not do it for the other variants!

Many fans of Frisian draughts are unaware that the most balanced setup on 10x10 baord would be one where each side has 3 first rows with draughtsmen, so the 4 central rows remain vacant. In this case, game becomes unlimited to opening choice and each side has sufficient amount of material (3 x 5 = 15 draughtsmen) for building positional or tactical advantage.

So, in FEN notation it is:
[GameType "40"]
[FEN "W:W36,37,38,39,40,41,42,43,44,45,46,47,48,49,50:B1,2,3,4,5,6,7,8,9,10,11,12,13,14,15"]

This way you'll only get "Stack up on the side positions", Positions with pieces in the center like in Long Diagonal or Bildtse opening (Which are most interesting and Difficult to play) will be comepletyly gone as you simply avoid center squares.

Yes the opening is unbalanced, I dont like that either. It could be balanced with a swap rule for white after maybe 3 or 4 Moves, or an Opening Ballot, with positions that allow creative play for both sides.