Interesting news! I'll admit that I'm not massively surprised by this, and I did wonder if that sort of thing might happen what with the park's change of target demographic.
I hold an unpopular opinion in that I think that adding a sit-down train might actually improve Shockwave. The standing position is certainly strange and not the most comfortable, and despite the fact that I'd always said that standing didn't massively bother me, my greatly underwhelmed reaction to my recent ride on Pipeline at SeaWorld Orlando would suggest that the discomfort of the standing position is more of a deal breaker for me than I'd previously thought.
It will lose some degree of novelty factor without the standing position, but I do think that lowering the height restriction to 1.2m and making it less "scary" by removing the standup train is a good move by the park given their new target market. Making it a sit-down coaster could carve out a new niche for it in that it could make it a nice "first looping coaster" for the slightly older children in the park's target demographic. I actually think a sit-down Shockwave would be quite well suited to such a role; it's not overly intense compared to many other looping coasters in the UK, it only has a few inversions, and it's quite a short ride if kids don't like it, but it's also a large enough ride that it gives off an impression of grandeur and scale to make kids feel like they're riding their first "big" coaster, if you like.
I'm personally interested to see what sort of train Drayton Manor goes for here. I could see a B&M floorless train; B&M do build trains for coasters that aren't theirs, and seeing as Shockwave is a coaster with a nigh-on identical track design to B&M's, I can't see it being too much of a challenge for B&M to build a suitable floorless train. The question is, though; would Drayton have the budget for a B&M train?