It's actually a possibility, if he want some cash in his pocket in exchange for a contract that is less favorable salary wise that will eventually be restructured.
The bonus is that he's young enough and good enough that you can give him cash out of your pocket without too much concern that he won't be around long-term. the biggest risk is obviously injury. But that's where having the league's richest owner helps. Usually this is the kind of deal you only do with a QB.
Look at Brady's contract for example, he only earned 1m in base salary in 2013 after restructure:
http://www.spotrac.com/nfl/new-england- ... tom-brady/
percys contract was for 14.5m guaranteed, of which he has already earned all of it (12m signing bonus, 2.5m base salary) so it's in his best interest to restructure for more cash directly into his pocket.
His contract is also for 6 years meaning that his final year has no deferred signing bonus money since it's only deferred 5 years (2013, 14, 15, 16, 17 @ 2.4m per)
He could be givin another signing bonus to restructure, that is guaranteed money in his pocket. We could for example give him a 25m signing bonus to restructure, just as an example, and lower his base salary by the same amount and then defer out the signing bonus.
this would put his current salary at an average of 5.5 per year and for the next 4 years a bonus number of 7.4 and then 3m in 2018.
Then you tweak his salary for the next few seasons so t hat it's back-loaded with the idea that you'll restructure again before too long, probably about 3 years.
So then you back load the contract to something like this
2014 base salary - 2m + prorated bonus of both contracts of 7.4 = 9.4 cap number vs. 13.4
2015 base salary - 3m + 7.4 = 10.4 vs. 12.9
2016 base salary - 3m + 7.4 = 10.4 vs. 12.3
2017 base salary - 8m + 7.4 = 15.4m (you would restructure again at this point, knowing you can defer out the prorated signing bonus of a new contract out another 5 years)
2018 base salary - 11.5m + 5 = 16.5m (would never see this due to restructure or cut in which case you incurr a 5m cap penalty)
Although these numbers are based on keeping his remaing salary the same. if you give a guy 25m guaranteed you can probably also talk them into reducing their base salary.
I'm no expert on this stuff but that is fairly accurate. whether or not it's realistic is another story.
the risk is that by converting salary to signing bonus in a restructure, you defer out that bonus money 5 years and if he say, gets cut, or gets injured and you have to cut him, then all of that deferred bonus is charged to the cap for that year.
You could do a less 'extreme' version of this setup and free up a million here or there though as well.