Yeah, size shouldn't matter, as you say, Condor send A320's, 753's and 763's just about every day and Air Berlin used to send their A333's down there every week. I've seen pictures of both Thomson's 737's and 757's there but the pictures of the 757's were taken on the same Tuesday and the 737's on the same Friday but now it is only 1 weekly on Fridays from both (in the winter at least) so it would make sense if the schedule has been reduced to round 1 738 and 1 752 per week up to 1 752 per week, also with the short (7200ft) runway the 757 would make more sense.
Sorry if that's hard to follow haha, if anyone knows for sure I would be very grateful, either that or if it gets booked I'm assuming you can select seats and look at the seat map so I could report back to here on what it ends up being.