With an elastic line, it may not be so bad.  Plus, a small amount of mis aligned rotation is not critical, except to the rule makers.   I would try and do it with one light, and 2 strings, rather than 2 lights.  

I have been giving this a lot of thought since we discussed it after looking at the Dutch barge while sailing Blind Date. No bearings, track or sail slides would be much easier and cheaper.  Main problem is that the mast could not be tapered.  Possible solution is a gunter rig, which also has some advantages in that the top mast can be lowered, which may or may not mean less drag when reefed.  The gunter could also be longer than the 6m fixed topmast as it would be lowered when not in use.  More height, more sail area and /or a shorter, lighter, lower loaded boom.  Maybe difficult to get a big roach, though.  There are issues with the hoops passing the boom attachment, but these are surmountable.  Also have to figure a way to easily hoist/lower the sail on the top mast.  Food for thought!   Any suggestions appreciated.

A much better location than the back of the mast. 

Which would be tedious, made worse if the outhaul was not in the cockpit.

Would not be too hard to manoeuver back on course, but 1) when the sheet is eased, the sail is no longer on the side of the mast, so it is not very efficient, although still better than a fixed mast, 2) big loads on the slides if caught aback and 3) hard to raise/reef/lower it unless the boat is beam to the wind.  

As are many 'simplifications'