So how do you plan to fill the 100 gallon aux tank? Having an aux tank to run off during an extended outage is really nice but that fuel eventually has to be replenished.
Unless you can get a fuel supplier to come out and fill it after an extended outage, around here its a 200 gallon minimum delivery, you'll need to deal with refilling a near empty tank at home.
Transporting & filling up Jerry cans at a station is time consuming and then schlepping them to one's generator location & hefting each one up above your aux tank gets old fast and can be messy. Then there's the cost factor associated with having multiple Jerry cans and the storage space they consume.
However, if you mount an aux tank on something like a Harbor Freight trailer (if you have room), or dolly that can be wheeled out of garage & onto a trailer or truck bed its then transportable. Pulling up to a diesel pump hose and filling up a 100 gallon tank until it clicks off is so much easier.