I've noticed some oddities if you place crops next to doors. They won't be watered by rain and can only be harvested while standing in the door. Also if there was a way to mark tiles within a farm area as not to be planted and/or for a specific crop when getting an NPC to tend your farm that would be useful. (Eg. The corners of the area around blueberry bushes)
Ah, if you plant a crop right in front of a door, that actually counts as indoors (hence why the roof disappears when you stand there). I'm not sure how important this is tho - as why would you plant a crop right in front of your door?
You can mark multiple areas you want (the minimum cost is based on the size of the region, so it's more or less the same cost for a few small areas vs one big one if you want an irregular shape). It'd be complicated to exclude individual tiles, but I could just add a rule for no planting crops in the corners around trees/blueberry bushes.
Forgot I meant to reply. The indoors thing makes sense. I've got my farms in a fenced in area wrapped around the side of my main house accessed through a back and side door. Also at some point after my initial post the NPC who was maintaining my farms stopped accepting quests until I tried to directly give the job at which point she immediately teleported to my farm and started working again.