Sorry for delay in your detailed reply.....due to size of Jet2's operation it probably makes sense to keep their check-in/bag drop in T2/Eurohub/South, I presume the stand that can handle A321 is stand 8 which has or used to have 2 airbridges (or maybe a stand between T2 and runway)?
Having never flown from T2 I am unsure how many bus remote stand gates they have, I did arrive once into T2 with Ryanair, I was shocked there was only 4 immigration desks with no automated immigration barriers.
The 13 T2 stands that can accommodate 737's, can they handle 737 MAX?
Re stands between T2 and runway conversion to MARS stands, these would probably be similar to T1 remote stands I guess (looking at Google Earth). Guess problem with low cost carriers moving to T2 is the capacity (e.g. baggage reclaim and immigration). Jet2 in March I departed from gate 56 (stand 57R) they did use the airbridge for passengers sat in the front half of the plane on departure but not on arrival despite parking on the exact same stand, as the lights in the airbridge were on I am unsure if there was an airbridge issue or if Jet2 chose not to use it.
Thanks for your reply but regarding 'enough stands with airbridges in T1 for airlines that do want to use them' I don't feel there is, in March or May I saw a Luthansa airbus on steps, a friend recently flew AirFrance presumably an Airbus steps, I have flew KLM on a 737 a while go via steps and TUI have to use a mixture of airbridges, non-airbridge pier served stands aswell as remote stands, when their preference would probably be to use the airbridges.
I am no expert but I guess on stands 42 and 41 the airbridge can only be used if the aircraft is parked on the centre (C) line, as the airbridges on those stands probably can't position towards the left (L) and maybe slightly too short or not configured to connect to the right (R), I know if there's too short haul planes on stand 56 and 57 (4 planes in total) the short haul plane that can use the airbridge is parked on the right (R) line, whilst left (L) will use the steps.
In regards to if you are on a low cost carrier and the plane pulls up on the airbridge stand but doesn't use it, you sort of guess its the airlines preference depending on the airport and circumstances. I am unsure what the protocol is regarding immigration/customs arriving from Ireland (Eire) but I guess years ago the Aer Lingus flights didn't use the airbridges on the newish (2009) International Pier as the arrivals route leads to immigration/customs when I guess they were exempt (unsure now).