My future 5D ? Does that mean the MkI II or the future MkIII ? If it's the MkIII you're not likely to get the option to change the focus screen!
So what camera do you currently have, and why do you need the fast prime lens?
The question comes across as a bit of gear headed money burning a hole!
Given that print professionals cannot tell the difference between a G9 and a Hasselblad with a phase one back, who do you think is ever going to notice? In fact providing you're not using the fast apertures, and testing around f/5.6 no one would be able to pick out one lens from another in a blind test !
You want to use this lens for weddings, I'm not sure a 35mm is the best focal length for that, but you don't indicate which other lenses you own, f/2 is not particularly fast, the canon is an f/1.4, lack of autfocus will mean you will miss far more candid moments than you capture, and that's about the only reason you'd want a fast prime. More formal shots should be made with flash / strobe lighting which you can control, and even outside it helps. You should perhaps be considering the 24 - 70mm f/2.8 L and a 70 - 200mm f/2.8 L plus some decent lighting.
Even if you use speedlites a set of three plus remote trigger light stands and modifiers will cost as much as a decent lens, but it'll make much more of a difference if you learn how to use it properly! Photographers like Annie Liebovitch are known for the quality of their lighting technique, and not the quality of the lenses they use!
(That & the fact she's nearly bankrupted herself!)