The HPV Spirit has no facility for a multi ring chainset on the front (not designed for a changer mech) so the only options are a hub, dual-drive or single cassette. I went the Rohloff route so front hub was a must. I is great but needs care when pulling away and taking slow corners.
In fact I have this problem with all my HPV recumbents as I don't have a front mech mount on the booms due to having a Rohloff because I like the neat clutter-free boom.
On my Scorpion fs I plan to fit a Schlumpf drive when I can figure out which one I need as this gives 2 gear ranges on top of the rear freewheel 8 speed I have at the mo. One day, I promise, I will take pics of all my electric bikes.
One day (I hope) someone will bring out a crank drive kit (like the Sunstar was) and I can use my Rohloff again.