A way prioritize could work with added utility would be as a trap.
Prioritize -

Instant
If Prioritize is targeting a spell you controle you may pay

instead of it's casting cost.
Copy target spell, you control this copy. If the spell had any targets, the copy has the same targets. Then exile the original spell.
Some things are more important than others.It gives it some more utility (say copying a tinker) but also forces the original spell to resolve in a tricky way.
The problem there is that you've printed a strictly better Spelljack even at full price. If your opponent plays Fact or Fiction and you Prioritize it then you get to Fact, and they don't (plus their Fact gets exiled, not sent to their graveyard).
What about "that spell's controller controls this copy."
Also, I'm not sure if the timing for your trap cost works. Does one announce targets before paying costs? Rigorously I mean? I think you do, since Wasteland 'can target itself'. Do you announce targets before determining costs though?