Yup. If the excellent Rail Map online (
https://www.railmaponline.com/UKIEMap.php) is to be believed, services would have to use P2 in both directions, crossing over south of the station (two crossings).
I can't see 22x or any significant diesel under wires proposal being approved, even if just two services per day.
Depends on where they call, I guess.
The xx.15 and xx21 are tied together, so that the XC at xx.21 overtakes the xx.15 stopper at Rotherham (Masboro v Central) - the only point it can do so between Sheffield and Leeds. I've seen the 17.15 held at Sheffield until a delayed 17.21 is approaching, so that it can't get too far ahead.
Here's a thought. The first service of the day starts from Hull, runs to Sheffield and on to London. The last service ends at Hull. That gets them to Botanic Gardens for overnight servicing. That might be an ECS move anyway, but why not a revenue-earning service (and providing an extra trip between London and Hull, if a bit slower than the others)?
Anyway: good luck to them