There are plenty of landsailers and iceboats that use stays (and stiff masts):

The biggest issue with re-using the cat sail is re-cutting it to be smaller and
much flatter.
If you look at the sail on the yellow boat in the photo above you'll see just how flat the sail for a faster-than-the-wind boat has to be.
If you'll be sailing on softer or higher drag surfaces (ex. sand) you may need a bit more draft/power because you'll be sailing slower.
Land and ice sailing is all about apparent wind. On a good surface the apparent wind angle doesn't change much from about 10 degrees off the bow on any point of sail.
If you watch the windex in a video of a windward-leeward course you can see it doesn't change much upwind to downwind:
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The apparent wind speed is also quite high. If you're sailing upwind in 10 kn of wind and going 20 kn (a pretty meager 2-times the windspeed), the apparent wind will be around 25 kn.
I can't tell from the few photos I looked at if the Windrush has a rotating mast.
If it does, I would suggest keeping that feature.
Cheers,
Geoff S.