Just a few things I've picked up here and there when I've read and toyed with the idea.
As I recall .. from previous discussions and such .. Stripping the Insight down gives you at most an upper of of around ~180kg to work with .. without gaining any OEM weight.
The biggest / heaviest part will likely be the battery.
I don't tend to use it that ay .. but I did once run pure EV-Mode in my PHEV Insight for ~4Miles on a flat / level road it took ~9.4kw 5th gear to maintain ~50MPH .. ~5.4Miles per Kwh .. and that included about ~3.5kw of all the Air pumping losses / Friction / etc , of rotating the ICE .. I had previously run tests of power usage not moving just using IMA to rotate the ICE .. or about only ~5.9 kw of actual motive push the car , ~37% OEM was used for ICE losses .. or without ICE looses would have been around ~8.6 miles per kwh .. I think this correlates to roughly about ~98MPG from OEM ICE in LB 5th gear on flat level (similar conditions) .. Soo I used those to get the MPG you average now divide that by 11.6 to get roughly the miles per kwh driven a similar way.
If you have a usable ~50Mile range goal .. and your MPG/11.6 = about ~5 .. conservatively consuming 1kwh ever ~5 miles .. that will mean you will need roughly about ~10kwh of usable battery capacity .. if you only use the middle ~80% .. avoiding the top10% and bottom 10% .. that would mean a battery pack of ~12.5kwh.
For comparison / example .. the A123 Pouch cells I used for my PHEV build are about ~120wh/kg at the cell level .. to get ~12.5kwh at the pack level from A123 Cells would likely come in around ~125kg .. leaving about ~55kg (if staying at OEM Weight) for all the rest , motor , controller , etc.
While at the top end (of commonly available wh/kg cells) one could do the Tesla modules route although not cheap , and but load of time ..
Link to get up to about ~212wh/kg at the module level .. a completed ~12.5kwh battery might weigh as little as about ~65kg .. leaving about ~115kg (is staying at OEM weight) for all the rest , motor, controller , etc.
MikeD drove around for a long time with several hundred extra pounds of weight .. soo ending up a bit heavier than OEM .. is also an option.
The OEM Insight ICE+IMA is a peak of ~60kw .. and peak combined ICE+IMA torque of ~91Ft-Lbs .. an electric motor of similar performance would have the same highway like performance , but better low end torque ability.
In this power /torque range .. the lightest (not cheap) electric motor I know of is the Emrax-188 to get ~70kw peak ~30kw continuous ~100nM (~74Ft-Lbs) peak torque .. and the motor is only ~7kg .. because it's peak torque is slightly less than the OEM Insight's you will not have to ever worry about over torquing the rest of the components .. but if finished near ~OEM weight you will have gained ~10kw of additional peak power , and better low RPM too.
Best of Luck.
