“Fixin’ to” is the national verb of Texas. Certainly you find it in use in other states, but it is particularly pervasive in Texas. For many of us it is the default verb for anything to do with the near future.
If you told me I couldn’t use fixin’ to, like many Texans, I would be grammatically paralyzed for a while. I have no back up at this position. I have no other verb sitting on the on the bench ready to go in.
Fixin’ to has it all – it can run, pass, stall for time and run out the clock.