1. I would use a RIX SA-6 for the compressor....clean air, no oil, modest size and power rrequirements, capable of 3500 psi.
2. I would continuously blend both EAN and Trimix .....being able to utilize all the contents of a supply cylinder and only having to have a lease on three: Helium, Oxygen and Argon.
3. I would have the compressor plumbed so I could pump Argon into an HP80 or HP100 storage bottle @ 3500 psi for use on the boat as well as for filling suit inflation bottles.
4. I would have a storage bank of 3500 psi cylinders for the mix most used (in my case EAN32).....this would allow filling and topping dive tanks without having to start up the compressor each time....especially since we use LP steels.
5. I would have both He and O2 analyzers fed by a sampling regulator off the main fill manifold for post-blending/compression analysis.
6. I would have quick disconnects on the Argon whip so that it could also be used as a fill whip for priming deco bottles with O2. I would have quality gauges and a needle valve on the fill whip as well.
This would just about do it for the garage.
7. For three day trips away from home on land I would have a bank of HP storage cylinders in the dive van.
8. For three day trips away from home on the boat I would have extra sets of dubbled LP104s.
I'm workin on it....