vent
IF done properly, and that is the key word, it will work, but why are you making your life so difficult? If you have another vent through the roof at the eaves, just connect the conventional toilet vent to it, in the attic, before it goes out the roof. The problem with a loop vent is that it does not always function as a proper vent until towards the end of the drainage cycle. With a toilet, which creates a substantial suction due to its volume of water, it could affect the traps in the other fixtures. And in any case, a loop vent is for an individual fixture, not a group of fixtures.