It worked beautifully!
I boiled the matodextrine in some water (4oz malto and about 4 cups of water) for 30 minutes, cooled it a tad and added straight to the keg.
The beer is immeasurably better. Incredible mouth feel (whereas before it was super thin). Much much better hop flavour and a little bit more bitterness, no real change to aroma. All of which is exactly what I was hoping for. Haha, hopping for. Get it?
Verdict: You CAN add hops post fermentation by boiling them with maltodextrine and adding to the keg/bottling bucket.