Our HS coach set up the pitching machine aimed at the basketball court and shot grounders at the field players. Boy, was he in trouble when the basketball team showed up the next day with a ruined gym floor!
Our team used portable mounds for pitching, set up an indoor cage in the auxilary gym for hitting, and clocked OF throws the length of the gym to get an idea of arm strength. Other than that, lots of 6am running and plyos when the gym was available. Think he was trying to drive off the boys who weren't committed to working hard. You just make the best of what you've got till the weather warms up!