Sales Experiment: Sale by License?

Just a random thought from this morning as I contemplated whether I really wanted to re-buy Braid for the 360 so I could clear it off my latop’s slowly shrinking harddrive:

Considering the increasing move on the part of the major publishers to sell game boxes under the auspices of actual software licenses instead of retail box ownership, would gamers be willing to spend an additional $X amount in order to acquire a truly platform-agnostic version of the game they want?  And would publishers be willing to make such an offering price competitive?

I can think of very few gamers I know personally who would want to pay full-price for a different platform SKU of a game they already own, but I suspect that at least some of them might be willing to pay a 10 to possible 20% markup on the original box price if it meant they would be able to transfer it, via download, to another platform.

Now, obviously, some kind of DRM would likely end up being built in somehow; Activision would never sell such a license for Call of Duty if it meant that some guy could “gift” his PC-installed-but-platform-agnostic license to his friend’s 360 or PS3, but we’ve already seen Valve experimenting with such a model with multiple Steam offerings (with no markup, even), using Steam IDs as the gatekeeper preventing license gifting.

Could this approach be applied to the traditionally stratified Console vs PC market, and would the major publishers (besides Valve anyways) be willing to experiment?