That could definitely work. I'm thinking about something around this line:
Trades in ladder channels would only be allowed to use LFG.
In order to get LFG, you'd have to convert FG (there'd be a converter box).
The converter box would adjust values depending on age of ladder season.
For example:
Day 1 FG to LFG ratio
1000:1
Day 350 FG to LFG ratio
1:1000
Values of items would still remain the same. So 1 hr on ladder (after they get duped again like alway

, but I hope they don't) would cost 5 LFG. (which would take 500 regular fg to convert into it).
Also notice I made :LFG be worth alot less than regular FG near the yearly reset counter. That's so people can't just convert their LFG back to FG and have another advantage in next ladder.
Sooner or later this would eat up alot of FG for those who try to benifit with JSP after reset instead of actually mf'ing like originally intended.