I dont mind it. Its very easy to upgrade your railjack and sigma mk3 weapons work good enough so I think DE can and should do it. Without grinding people gears tho. We are on global pandemic and people doesnt want to play warframe (even its minority its important).
Easiest way to integrate railjack is making it our 2nd orbiter. I said second because replacing orbiter wont work thanks to customizations they gave. It would make people angry.
If they integrate it, ı needs to be done very carefully. Imagine you started spy mission with railjack, guns blazing, blowing ships and fighthers next to galieon, just to board said galieon and extract data. Plz no.