I came up with a 1:2 spinnaker dousing rig over the winter. The main idea was to provide a way to leave part of the dousing line threaded in order to speed up rigging time. It also helps collapse the sail quickly - I had some complete beginners on the boat this spring douse smoothly with no problems. The rig uses a small line that is attached at the top and bottom grommets and runs through a small "kite block". The main spinnaker halyard/dousing loop attaches to the kite block, runs through a cheek block under the rear beam, through a turning block forward, and up through a grommet in the tramp as usual. It gives you 1:2 advantage until the spinnaker is collapsed, and then 1:1 while stuffing.

If anyone is interested, I'll try to provide some diagrams/pix. I wouldn't be at all surprised if this has been done before.

I have an end-pole hoop, so I'm not absolutely certain this will work with a mid-pole hoop (because of the ratio of the distance between grommets to the length of the trampoline), but I suspect it will.