Go to your bike shop and ask about more gears. You can get a 7 speed cassette with a wider range of gears (I've got 12-32 on a bike I'm trying to sell, that's a 7 speed). After that though, ask about a double or triple crankset which help make best use of your rear cassette. You're probably best off going to more than 7 gears but you're heading into territory where you'll need new shifters.

An alternative is to buy an old bike with the gearing you want and just change it over. If you're lucky enough to have a community bike workshop nearby, you can probably source second hand parts there too.

An expensive but practical solution is to get a Shimano 8 speed hub built into your rear wheel. Those things need little maintenance (just oil the change basically) and would suit the lifestyle you describe.

The trouble with all the alternatives is that it can get expensive in a hurry if you're not careful, then again, I can't imagine electrifying your bike is cheap.

You'll find that the most cost effective way will probably be to buy a new bike so don't ignore that option.

As for motors on bikes, personally, I can't see the point. Buy/build the bike for the job and you don't need the motor, but people will get upset with me for that.