Answer one questions: "where is the sheet coiled" and lead in the cockpit when you are close hauled?

You have multiple positions where you are trying to release the sheet. You might be forward of aft of the fixed main sheet attachment -- and you'll likely be off to one side a bit. It would different if you're singlehanding vs. having one or more people in the cockpit "doing things" or not watching....

I'm not sure there really is a better position without a traveler unless you want to limit the positions you can easily trim the main sheet from. You might add another "fixed" block with a cam cleat -- but as other have suggested, I think that only adds another thing to hang-up if you want to unload the main. Also, you're asking for trouble with that main sheet coiled around your feet, ankles, or legs. You' don't want a loose sheet "grabbing" you or one of your guests or crew that gets "drawn-into" some unexpected drama. ;^))))

Have you considered installing a traveler in whatever fashion the boat was originally designed to accommodate? How do those work in comparison? Do they run across the cockpit seats or on the "floor of the cockpit.

The other option, which I don't suggest, would be to raise the position of the block attachment a BIT so that the cam cleat is up a few inches. I really would be concerned with torqueing, twisting, and other complications.