If you want a shot at the most valuable players, you have to groom them yourself or pay out the nose. I like that.
Random related ideas. Consider the over-all effect when a few are stacked together.
1) Reduce the number of prospect discount contracts rather than reducing the discount (or term) itself. By limiting discount eligibility to players that have been drafted through the keeper (or supplemental) draft you would cut the number of discount contracts in half. It would also greatly increase the value of picks through the 3rd round.
2) Make discounted contracts non-movable. If discounts include a NTC how would that affect their value? Do GM's really want to commit to term on an unproven prospect if it is now not trade-able? If supplemental picks are made the only ones eligible for discount, and those same prospects are given a NTC, their value would skyrocket.
3) Drop the 3rd round supplemental (or keeper) pick. As it is the league is awash in picks and prospects. The leading teams all have assets to burn so it is really quite easy to 'pay out the nose'. Sharp GM's know that prospects are plentiful as we can quickly re-load with at least six new picks every year. When re-stocking the cupboard is so easy it makes sense to move out assets in bulk.
4) Let GM's relocate their franchise. Opening a window that gives us the option to move once every 5 years would let GM's move on from franchises with poor drafting and development (especially if keeper picks we're the only ones to be discount eligible). It will also refresh and inject life into franchises (GM's) that are feeling stagnant. If a GM decides to stay put they would not be able to re-locate until the next 5 year window opens.
Probably this is all too much but I wanted to put it up against the chatter about reducing discount term to 3 years. There are a lot of other approaches to look at.