That sounds like a really cool build; I'd love to do something similar if I were to start again.
You are right, rolling the lip does compromise arch liner mounting points. I removed mine quite a while ago, so that didn't even really occur to me.
Despite this, I ran fairly wide wheels without any archwork for quite a while. I'd go ahead with your 245s, and then trial and error the fit from there. Have a few 3mm spacers on hand! There's even variation from car to car, so you can never 100% predict what will arise in each case.
Why not test fit the wheels without tyres to gauge how much internal/external clearance you have to play with?
For reference, in my signature I'm running 18x9 +16 225/40 on the front with only a lip roll. Also, I've just noticed you're looking at 40 profile rather than 45 profile. I'd propose going with the slightly meatier tyre; it'll look much more factory.
Edit:
This car is running [F] 17x8 +30 235/45, [R] 17x8 +30 245/40, and seems to have loads of arch clearance all round. Remember, the lower you go, the more horizontal fender clearance you'll have, as the wheels will naturally camber in.
