I get it, as a 148 pound rider who has a 46 pound bike with a 250W / 40 Nm motor, I had a similar strategy in terms of figuring the power-to-weight ratio, though I needed a more trail-oriented bike. For a commuter bike, this might be fine for you.
Just be careful if you live in an area with a lot of hills. I'm crazy about my bike, but I just finished a 27 mile run with 3,650 feet of vertical yesterday, a lot of it on dirt.
I won't lie: It was right at the edge of my physical capacity, and I've been training all winter. (I'm 64 and have some health problems, but generally quite fit.)
Often, we wind up wanting to go a lot further, and to more challenging places, than we thought we would before we bought our bikes.
Lighter weight is important for lighter riders, though, I agree. I do have to push the bike up one nasty dirt hill that I'm not skilled enough to ascend, and also have to lift about three or four feet off the ground to get it over one gate on a run I take regularly. Also, I think a lighter bike probably handles and stops better for a lighter rider.