At our brewery, we have been building our own glycol systems using this type of technique since we opened in 2015 ... and we've learned a bit about how to do it safely.
Couple of quick comments about the power of the resultant systems ... basically the 12K BTU rating of that unit being used is relative to the design of the unit and being an air-to-air conversion in the specific temperature ranges it is tuned to operate in.
An unmodified unit running an air-to-glycol conversion will actually be more efficient in the target temperature ranges ... basically 60F to 90F or so.
As the temperature of the bath drops, the efficiency will be reduced. The only way to really know is to measure the rate of temperature change of a known load of liquid, then do the math.
However, as a general reference for how much power you need, we are controlling 2x 10 BBL fermenters using 2x 8K BTU ACs we got from Walmart. We crash from 55F (diacetyl rest) to 36F (crash) overnight.
That 12K design is probably capable of mainting a small army of 1/2 BBL fermenters ... like maybe 60 of them even if 30 of them were fermenting all at the same time.
For my pilot setup I'm using a small cooler and a 5K BTU unit. With a small foot print cooler with a cut into the sidewall, you can cut down the case of the AC and basically slip the cooler under the pressure lines without bending them.
We have also built a total control system based on Raspberry PI that will be productized for the pro and homebrew markets. Platform is still maturing, however we get to do things like watch and control what's happening in our brewery from anywhere ... fun stuff!