I'm not sure if I understand you correctly, but I think what you're contemplating has been done like below:
Pic of 'screacher' furler on sprit
http://www.sigi.ca/hi5/pictures_f33_...-2323_IMG1.htm
various pics of rigging ideas
http://www.sigi.ca/hi5/hi5/ads_72.htm
I myself have Amsteel halyards with what I'll call a 'working' side and a 'standing' side. These are made together with two long thin eyes. Crew pulls the halyard's standing end down to the eye, and then there's a downhaul/cunningham at the mast with a hook that's put through the 'working' end eye of the halyard. Tension is then achieved at the mast via the downhaul.
pics of my rig:
Screacher downhaul
http://farm4.static.flickr.com/3214/...e18_z.jpg?zz=1
Jib downhaul, showing the two eyes in the halyard and how it hooks:
http://farm3.static.flickr.com/2318/...588_z.jpg?zz=1
hope this helps