You can do a trial simply by removing the outer and inner rings, and using track chainring bolts to hold the middle ring where it is now. Then either remove the FD entirely, or use the limits to lock it in place over the middle ring as a chain keeper or sorts.
Or remove the remove the outer ring, and file/grind all the teeth off, and file a bevel to the inside so it serves both as a bashguard and cyclocross style chain keeper.
If you later opt to spend dough, you can source a dedicated single crank and BB appropriate to your needs.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.