been there, done that. ethanol is way easier to scale. Stills are well developed tek. Rainier knows stills and cannabis.
got a 100gal vac assist still I’m working on spinning up. started at 5 gal and worked my way up.
I guess technically I started with 2" of 1/4" copper tube bent in a U that I picked up and used as a condenser on the vent hole of a rice cooker lid when we were making RSO many moons ago. the proof of concept lasted until the copper exceeded my pain threshold at around 70C and I dropped it 
For a while I had a condenser soldered to a mason jar lid, and could recover solvent at several different scales, from 4oz to 64oz using a rice-cooker as a double boiler.
My current 26 gal still was probably $2500 in parts. All off the shelf except for the boiler and it’s controller. the boiler uses a ~3gal tank salvaged from a commercial chiller…it came with level senders, thermocouple, temp and pressure reliefs etc. Grabbed the SSR’s to drive the heater as well. I threw a 5500 watt water heater element in there, and use a cheap PID controller to keep it just under a boil.
The big one was less than $20k for two 100 jacketed vessels, still head, condenser, vac pump, and air powered agitator. $40k if you add the heater and chiller.
100 gal keeps me under the 120gal Ethanol in a CLS limit in my juristiction. Your mileage may vary.
I suggested the spray-vap, or a falling film rig, but the price of admission was deemed too high.
It was supposed to be installed as part of a hemp processing operation, ON the farm, where I could have reused well water for cooling, and then to water the plants. It was relocated to the city, where we’re going to have to pay for electrickery to cool the condenser rather than throw water down the drain.
Vac assist requires agitation, once I have the big still up I’ll probably try adding agitation to the smaller still as well. Although if I can find an off the shelf 8" product shot-gun for the right price, I might add a recirculation pump & try a DIY falling film.
As far as burning crude goes, I stop early and finish in a rotovap so I can control the product. It’s pretty difficult to burn anything if you’re using hot water to heat. And you should be. you really don’t want direct heat, or any electrickery around your 190.
My 100gal still has a 10" manway at the bottom, to allow the operator to get a spatula in there to move product out the drain hole if they accidentally “finish” in there. This was suggested by the supplier, who was heating their prototype with steam, and had a major problem with removing too much solvent.
The 26 gal one is based on a jacketed conical fermenter, and does a great job of delivering the goods into my 5l rotovap flask when it’s done. 26gal still is driven with 96C water & takes about 12hrs to recover 15gal. Product is fully decarbed at end of run. loading less than 7gal results in a partially decarbed product. Haven’t looked hard at losses to thermal degradation, but have not seen CBN showing up on my 3rd party testing (ask a stranger) or in-house analytics.
With the 100gal version, I’m running vac and aiming at 35C in the boiling vessel, theoretically I can hit 25C if I suck harder. no clue what recovery times are going to be. hoping I can get THCA out of it. would be nice if I could also get decarbed by running at the right vac level.
I was concerned that scaling would lead to long dwell times at temp, but pulling a vac solves that problem. not sure an off the shelf 500gal still is going to take 25in Hg. I did propose it at one point. as a solution to the 500lb of accumulated cannabis in the corner. “I can process that in one day!”. I don’t remember the exact numbers, but it was something in the range of $200k including solvent.