Couple things...one, are you planning on adding a central brace? I would be...most 125's have a brace in the middle, and you should support that.
Another point is that I have a 125g with dual end doors on the base, and although it was good for putting the sump and other stuff in, I would suggest screwing the door into place afterwords. My 125g stand is over 3' tall, and before the doors were screwed on you definitely could have knocked the tank over if you had wanted to. (Or if a small child had gone hurtling into it.)
Plans look awesome, I hope that you are fairly experienced at carpentry, because it also looks fairly ambitious. I hope that it works out that well. :)