This is certainly a not ideal situation, but if those time constraints are your time constraints, there isn't much you can do. One thing that you can do is start to do your press/bench warm ups in between your heavier squat sets. Maybe that will buy you some time. You can also abbreviate your upper body warm ups depending on what weight you are lifting. Honestly though, I don't see anything wrong with this. I think that it is a reasonable adaptation to allow for time in the gym. I would have to reference the 4 day Texas Method split in PPST when I get home, but I believe the length of time it takes for the Texas Method 3 day is addressed by making it a 4 day program. So basically you are taking a page out of Rip's book.