I think the OP is really looking almost strictly for FE. He drives 300-1000 mpw so a difference in 45-70 mpg for a car that has alot more oomph, is going to make a huge dent in is his budget. Also a 2009 TDI starts at 22K with epa of 41 and the Insights can be had for 10K without substantial wear with an epa of 70.
If I am going to pick a place to start modding for FE I'm going to start with 70. Its not impossible to get that out of the TDI, I'm not saying that. But it will take some effort to get from 55 to 70.
Also with the 10K in savings you could coat the Insight in really expensive solar panels that will mount flush(flexible) add 3 more reasonably sized motors and have an EV for around town that passively recharges for free, or drives for free for the first 40 miles-60 miles on a battery pack(not the stock one) then switches to gasoline until the pack is fully recharged by passive recharging(regen braking and solar) and then switches back.
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Here you go. Sell off the engine and trans if you like and save the weight. drop 3 more 10Kw motors put them on the wheel hubs, add a much larger power back to get you 100 miles(I think the Insight can get away with 20 hp at 60? so 20 KWh. If you can find them in wrecked Priusae that would be the way to go otherwise you own't get the ev range) and slap solar panels all over it.
500 miles per week is 100 per work day. So assuming you do all the driving all at once you need at least that much power(20 KWh). The panels would boost you outside the danger range of the batteries if you drove half parked and then drove back. so 50 miles in the morning and 50 at 5, you could recover 8 kwh to keep the batteries outside of the below 50% range.
Seriously lol Buy an old insight sell off all its ICE parts(radiator, diffs, trans, fuel pumps, muffler, catalytic converter, ecu,) rip out everything you can't sell(intakes, exhausts, fuel tank) You can probably make back a grand parting that out, find 3 wrecked insights and buy their IMA motors and bolt your 4 IMA motors to the wheel hubs. You scrapped 3-400 pounds of just engine and trans plus other little tid bits. The weight would be well invested in battery packs and solar everywhere.
If your driving is more round-trip lean towards solar more than battery packs because the solar can recoupe almost 50% of your spent energy on a sunny day(9-5 work day). If its usually a shorter stay at work or longer range(more than 50 miles to work) you'll need lots more batteries and probably a charging station at work.
If you really want to go for the gold. . .Leave your house as soon as the suns up and stay at work until you have just enough time to make it home without flipping on the headlights. Then you maximize recovery between trips and then just have to pay the power company to recharge it overnight. So you get -50-70% of your charge for free and pay for the other 30%.