Dave,
Most sailboats don't have internal (inside the boom) mainsheets. This is because of the wide range of angles that occur between then boom and the mainsheet at the different points of sail. If you're thinking binimi, I'd consider not leading the mainsheet forward, and replace one of the blocks at the end with a ratch block - or a becket with a cam cleat if you feel comfortable with that. If you get a chance, check on the mainsheet on Precision 18 and 21's, they are rigged in this manner. The weekender sail area isn't that big; so moving the mainsheet attachment points shouldn't be a big deal.
On bigger boats, with dodgers and binimi's the mainsheet is often attached forward of the companion way and the sheet led back through the dodger.
If you're not going to rig your boat until the ice is out, you could always go up to Lake City and check out the different options used on the big boats. When rigging a boat, size doesn't matter as much as convenience.
Good luck