Aventon Soltera.2

From what I've read the answer would be no. Firstly, hub motors use freewheels which screw on, not cassettes. The Soltera .2 has a grip shifter with indexing for 7 speeds which would have a different spacing then an 8 speed, so it would not play nicely with your derailleur. You can find a 7 speed freewheel that has different size sprockets. Drift Maniac makes an 11 to 34 tooth if you are looking for a smaller high gear and a bigger granny gear. This is popular with ebikers. The price is between $25 and $35 dollars depending on where you pick it up.
Thanks, Annieolnie.
Actually, I was planning on switching to thumb shifters and an upgraded rear derailleur anyway. Easy to go 8 speed instead of 7. Gives me another gear to put the "shifts" closer together (I'm still a Roadie at heart). If it doesn't work I'll probably get the freewheel you mentioned. I was already looking at it for a higher and lower gear.

Thanks again for the info.
You are welcome. Don't know if you've watched Path Less Pedaled on YouTube. He has adapted a number of old style non indexed shifters to different derailleurs and cassettes. He's a roadie who has opted for what he calls, "party pedaling", the concept being more fun less stress. You might like some of his ideas. Good luck.