Not really. Colonists build their end of relay and here we go, God-Shepard to the rescue.
A Mass Relay, particularly one capable of reaching its twin millions of light years away, is not a simple construction. The Primary Mass Relays in the Milky Way can only reach a few thousand light years, so the Mass Relays connecting the two galaxies would have to literally have thousands of times the energy output. Plus unlike the Milky Way, the people in Andromeda would have no galactic infrastructure to help in the project, so it would take them even longer if they could do it at all. If the people in Andromeda were in that much trouble, the resources would be better spent on defending themselves.
Well whatever Asari, Salarians and humans can do, Godshep can improve on it. Think of how much more advanced GodShep will be in 250 years!!! Heck, to be more realistic if the council can pull off and construct and intergalactic ship in secret and under pressure in a short space of time, the most likely case is that Godshep is already in Andromeda when our pathfinders arrive!!!
Regardless the information transfer is supposedly instantaneous, so being able to pull down super advanced technology would be a massive advantage even if the milky way contributed nothing more.
Unless you want to open a giant can of worms, it is much better to keep the galaxies separate.
I don't know. If the ship we're using is using Reaper or Reaper-tier tech then I don't see the Milky Way developing an even faster ship that would catch up and overtake ours. After all, the Reapers had at least a billion years to reach the speed they currently have. Now if we don't use Reaper tech, then yes a ship from after the Reaper War could catch up and overpass us.
I don't see the problem in us getting technological advancements from our home galaxy. If it's anything major like how to build a way to allow instantaneous travel or anything else you're worried about, then the problems I stated above apply.
I'd much rather open that can of worms than keep the galaxies separate. I want this part of the MEU to be connected to the Shepard Trilogy.