I played a period of the Frozen Four 2007 mod just now to try it out (5min, no penalties, no offsides, no line changes). I appreciate the effort to make the time scale more appropriate to real time, as I always feel like there's not enough time to mount a comeback if you're losing in standard NHL '94 time. That being said, I feel like there's the opposite in this FF07 mod: there's too much time now. In just one period against the computer (U. Maine v. UNH) I had a 4-0 lead...which isn't much different from what I could get in a standard-timed period. I feel as though the speed of the skaters balanced well against the speed of the clock in standard time, but in a realistically-timed game the skating speed isn't scaled to reflect the time change. I also don't feel like the gameplay is really any different from standard NHL '94 play; not being familiar with this FF07 mod, I wonder if the weight bug and C/B bug has been corrected or not.
I decided then to play a game with penalties and line changes on, and I think I see more of what you're getting at. The biggest change is players getting fatigued more quickly and that affects their speed enough to offset the game clock change. Where I see a problem is when you have a power play, the fatigue becomes too much of an issue as the penalty wears on, and then you have two teams of players sluggishly puttering around the ice, and then when the penalty expires both teams will be in a hurry to put out a fresh line. I'll have to try a few more games to get a better feel for it, but the lack of extra lines/players to accommodate for this sluggishness is where it needs improvement.