I bought my J30 in 1985 primarily for singlehanded racing. There was very little that needed modification. I had the bow pulpit modified with an additional rail about halfway between the deck and the top rail (so that I couldn't fall through it) and had a 1/4-in. stainless crossbar welded inside the front of the top rail so that I could attach halyards to it.
To keep headsails on deck I drilled holes through the toe rail so that I could have light line lacing on the lifelines as far back as the second stanchion. About 1 ft diamonds. To securely hold the sails down I attached 3/8-in. shock cord with plastic hooks port and stbd from the bow pulpit through the first stanchion base to the second stanchion base.
When lowering a sail, I would make sure the halyard was free to run through the rope clutch and turning blocks, then pull it forward from where it exited the mast so that I could control the halyard while I was on the foredeck.
Singlehanding the J30, you reef and change jibs based on autopilot performance. The main thing is to keep the boat balanced so that the autopilot doesn't self destruct trying to maintain course. The boat is hard to sail flat in much wind because there is no crew weight on the rail.
There's more, such as schemes for getting aboard from the water, disabling the autopilot from the water, etc, but I think the major issue as far as singlehanding the boat is concerned is changing jibs.
