Assuming the worst case scenario where Tali isn't able to adapt to Shepard so their physical contact must be extremely limited, I'd expect it would be like a real life long-distance relationship: difficult, but possible if both sides are committed enough. It would actually be a bit easier since at least they're able to cuddle with the suit on.
That said, from what's been said in the game so far it seems likely that the physical side of things would actually get easier over time.
Kaiser Shepard wrote...
Let's say there's a mid-game romance section in ME3, where only a little (optional!) physical contact takes place: a logical, albeit unintended outcome of going "too far" with Tali would be her getting a severe fever, resulting in an extra scene or two at the gameplay 'cost' of her being out of commission for the duration of one main mission/planet. Obviously, one wouldn't expect Jacob or even Liara to be able to get in a similar situation.
You know, I actually would like that, just for the realism. In fact, this always bothered me a bit in ME2: after the ending, Tali says she's feeling sick but it was "totally worth it". However, she was fine and able to perform as normal during the suicide mission! That's an awfully convenient delayed reaction there.
For realism, it would've been great if physical contact either took Tali out of the picture for the SM or reduced her performance somewhat. Of course, if they went that route there should've been an option to avoid taking her suit off while still having a romance scene with her.