..except for all that has already died while being signed up.

It's not like they're going to be in a position to lobby for it. And there's a world of a difference between a paying customer or potential customer and a will or foundation. The wishes of the dead are frequently flouted when convenient today - look at what happened to Nabakov's manuscript.

In any case, in the event that radical life extension is already here, there's just no need to solve the problem of defrosting frozen brains for paying customers so I'd expect that to be, at least, put on the back burner. Re defrosting today's individuals in the future for academic interest - given the amount of documentation of contemporary life, particularly when compared to the 19th century, I doubt that today's future frozen brains would hold much interest for future academics. And remember, we'd be talking about a time when radical life extension would be possible so there's bound to be plenty of methuselahs around to talk to - why bother going to the effort of figuring out how to defrost?