Definitely possible, but of course a compromise.
A foilwing sized say 1500 to 1600 cm2 (for average weights) works fine for both kite-surf-foil and wingfoil when a bit experience.
As most drop from the big 1800-2000 cm2 foilwings down to smaller foilwings, unless in marginal winds.
And many use 1000 to 1600 cm2 foilwings for kitefoil in waves or freeride fun.
The compromise will be your kitefoil board will be a lot bigger than needed.
This is not that bad though, as I assume you will wingfoil when windy, according to your post, and kitefoil when lower winds.
Here a bigger board makes sense anyways, in terms of paddling ashore if wind dies, and you can also start in a bit less wind, and get through mega lulls without getting off the board.
A bigger board is not heavier, it can be made lighter in fact, if one wants that, as it is thicker.
So the "feel" of a bigger board when not heavy winds, can be really "light and effortless", and feel like no swing weight, if superlight.
But catch the edges somewhat, if carving hard or waves.
If you want the board a bit more bomb proof for wingfoil in higher winds, then you will have a board which feels heavier than a kitefoilboard when carving, yes, compared to our usual small boards.
But definitely doable - only you can find out when you have tried it.
Of course, a "normal" big wingfoil board and foilwing, can also be used with a kite, but I think, having tried it myself, it feels way off, too big a wing and too big a board.
I dont want such a small wingfoil board and compromise myself, so I have to go with different boards for wingfoil and kitefoil.