Good spot Shy. But this is just nuts. So many points:
The amount of admin time to request a Class D transit on line is quite significant - I'd guess 5 mins. And that's a lot. And as you say, many of us don't have ops departments.
Many of us don't always have ready on line access to do this. The 3 or 4G coverage is far from good when away from wifi. Then what?
What routes you get are clearly influenced by other traffic, so you may well get another to that requested.
A lot of flights cannot be timed to even within 15 mins - we go when we're ready, we're not scheduled flights.
This just seems sure to create more admin work overall, given the inevitable lack of precision of routes and timing, thus usually ATC will have to rely on the initial radio call info anyway to approve and route.
If pre requested transits don't have to be cancelled and just fall away if not used, how's that going to help with accurate co-ordination of busy airspace? Requests might be refused because someone else has pre requested it - and never shows.
ATC controllers also sensibly take into consideration the apparent competence of the pilot from his RT before issuing clearances.
And that's just a start!