Thoughts on running AT&T v6.0.1 while using Cricket?

[AMG1978]

I owned a Nexus 5 before which had vanilla Android on it. In order to use Cricket I had to modify some settings like the Access Point data. For AT&T I had to do nothing... Since I got my S6 (which is an AT&T branded, unlocked), the first thing I did was wipe it using Odin and install the Cricket v5.1.1 image. I want marshmallow and thinking Cricket may never release it (I am told though that AT&T owns Cricket now?). I'm wondering what would happen by running the AT&T image with the S6, on cricket? Will it work? If so, what would happen when trying the Tethering, would it fail like it does now as I am not paying $10/mo more just to tether? I do miss the Nexus 5 in that respect

Edit: now that I am looking at the rate plans for T-Mobile, I'm considering jumping ship. Seems the same LTE bands (actually more listed for the ATT S6), so it seems it should map right over. Hmm... I do not enjoy the always throttled on Cricket to 8Mbps max.