Fair enough. So, for paper (which is flexible, as well as dimensionally variable with humidity), wouldn't you want to go with the Timeless rather than Polycrylic, so that it can move with the paper as it expands, contracts and flexes, rather than staying rigid?
Timeless being very slightly yellow when applied to paper isn't a problem - a simple profile can fix that. It's yellowing over time that you can't profile for - I thought Timeless was supposed to not yellow over time.
I guess another advantage of the Timeless is that it makes it safe to ship the paper rolled (something I wouldn't do with a print on coated paper sprayed with Hahnemuhle Protective Spray, for instance).
So, you've noticed that Timeless seems to penetrate deep into the paper base, through the inkjet receptive layer? Sounds like a good sign, then - if the spray laminate, inkjet layer, image and part of the paper base all all basically embedded in a single, thick layer of Timeless, then delamination and cracking should be next-to-impossible. Is this with undiluted Timeless, or do you have to thin it with water?
How does it dry? Does it dry like inks, soaking in through the paper to the other side, or does it dry by evaporation from the sprayed surface? If it's the latter (meaning that carrier chemicals won't get trapped in the paper, between the two layers of Timeless), have you thought about spraying the reverse side as well, to prevent curling and to seal the back of the print from humidity and atmospheric pollutants?