Ok Some observations.... First, there is no reason for a 2 stage pull. This process is a crutch around inadequate vacuum sources on smaller home machines. 60 gallons of total tank is a nice size, if you do smaller parts on the machine, and you will, you will find it handy to put a valve on the tanks so you can get 20 or 40 callons as choices. This will make the job go faster when you dont need to pull down a large volume.
The heater needs to be zoned. you need to be able to control the heat in local areas to make complex parts. Its easy, add switches and change the coils to make them.
Reality ssays something different though... Build good tools and job it out.... the money is in sales unless you want to build a lot of plastic parts for a lot of people.....