The TCU athletic director has publicly stated that TCU's administration opposes the admission of any additional Texas schools to the MWC. The reason for their opposition is marketing related "product separation". Eric Hyman's words not mine. Although Hyman is long gone, the TCU administration has a long institutional memory, in my experience. They have not indicated a change in their position on admitting Houston or anyone else based in Texas, and their reasons for opposing the admission of Texas teams still exist as far as I can tell.
On the other hand, I have heard absolutely nothing from official TCU about inviting Hawai'i into the MWC, or not. So I really have no idea what their position is or would be.
I never made a TCU football game in Hawai'i, so I have no first-hand experience with Hawai'i fans. I did hear a lot of grousing from TCU fans that made a trip to Hawai'i about dangerous, thuggish fans. But the TCU fans I'm thinking of would not be the deciders on TCU's position on admitting/excluding Hawai'i from the conference.