I can see lots of problems with that setup besides the inconvenience of sitting around the winches.
The lead from the jib turning block to the winch itself is very flat - you must get occasional overrides unless you only ever use a single wrap during tacks.
Do your spinnaker sheets use a forward fairlead in the coaming or do they have to go out and over the coaming edge? All that stuff looks awful busy there.
As to your jib winch, I'd probably build up a pad against the coaming (inboard, as it looks like no deck area outboard the coaming), raise the winch enough for the drum to clear the coaming top, and move the jib turning block to just behind the fairlead in the forward coaming, on the seat. Then the sheet would enter the cockpit, turn on the block and up to the winch - a better angle of approach. The winch would be higher relative to someone standing on the cockpit sole and so easier to grind too, though a bit of a reach further outboard. This would allow you to preload the winch with a couple of turns without risking an override.
You'd have to relocate the jib sheet cleat too, of course, but that would clean up the cockpit seats. You would lose a bit of seat back in the area where the winch/pad would sit, but that might be easier to avoid than where it is now.
We do occasionally get over-riding turns..
From the spinnaker block on the toerail, the sheet goes through a fairlead aft then forward along the inside of the coaming to the turning block with the others (apologies - I should probably have rigged the spinnaker gear, but we don't use it much). The downhaul doesn't need to use the winch, so - yes, I think what you suggest is possible.
I'd need to put the winch somewhere it doesn't stop the crew leaning out (over the coaming):
1. How high should I (would I need to) mount the winch? I've seen other boats with it mounted above the coaming, but it seems to me that the higher you get the more difficult it is to mount it rigidly.
2. Where/how would I mount the turning blocks? ie. what is the correct angle for the winch?? - this would probably dictate the fore/aft position of the winch..
3. Where/how would I mount the cleats?