It needs to be half a Bolt, i.e. the Bolt's MPGe and 1/2 of a Bolt battery so that it has 120 miles of EV range plus the same range extender as the Gen2 which needs no improvement. The bigger battery could be an option because there are people that don't need the extra range but for many people, myself included, the current range is grossly inadequate. At 1/2 Bolt the car would be a true electric for all local driving and would only need it's gas engine for road trips. In a perfect world there would be a BEV with the same range as the Volt, 450, at the Volt/Bolt's price but that simple isn't possible with the current battery technology. To get the Volt's range today you would need a ton of batteries which is counter productive because most of the time you would be schlepping around all that weight for no reason which would hurt your MPGe. Batteries with 2X the energy density of the Bolt's batteries could be 10 years away (hopefully sooner but the historic rate of battery improvement is 2X per decade), so it's impossible to build a good enough Bolt until that happens. However it is possible to build a good enough Volt today. The battery pack in the Bolt is 900lbs, a little more than twice the weight of the Gen2's battery pack so if you took 1/2 of that pack, 30KWh, and coupled it with the other improvements that they made in the Bolt which has about 15% better MPGe than the Gen2 Volt, you would have a Volt that could go 120 miles on the battery and still go anywhere which the Bolt can't do. I think 120 miles is the magic number for local driving. I look at all of my local trips, to Boston, to Rockport, to Jaffery NH, they are all 50 to 60 miles so 120 miles would cover the round trip. My longer trips, which I do every weekend in good weather, would still require the engine but in the Volt they are perfectly doable, in the Bolt they are undoable and in a Tesla, which has a rudimentary fast charging network, they could only be done in a 100D, which costs more than I paid for my house, plus a lot of planning.
Aside from the greater range it would be nice if they offered the standard amenities that you expect in a car in that price range, i.e. power seats, moon roof, AWD. I would certainly pay extra for AWD and power seats. The styling of the Volt is fine, I would expect the next one to be tweaked a little bit to match whatever the styling for other Chevy's is for that year, but the current Volt is vastly more attractive than the Bolt.
Giving it a little more thought, it's time that they introduced a range of Voltec/Boltec cars. By that I mean in addition to the Volt offer a Malibu and an Impala all of which have the following options,
Hybrid, i.e. ICE plus small battery, maybe a little more battery than the current Malibu hybrid so that it can do 30 miles on battery which would still be better than the Prius.
60 mile battery plus ICE, Voltec
120 mile battery plus ICE, Voltec
240 mile battery, no ICE, iBoltec
One of the Volt's main problems is that it's too small. I've come to like the small size, in a world of parking spaces that have been laid out for monster trucks it's painless parking the Volt, but most people prefer larger cars.