Good point, and hopefully it's *really* strong. But, I guess my main point (in support of the built-in battery idea) is now that these devices are so low power, it would actually be possible to put a small-ish battery in which could power it over small 'accidents' or the more likely brown-outs and such that people w/o UPSs *WILL* experience over the years.
Ironically (to the supposed purpose), I've never had a MagSafe connector save one of my many MBPs over the years. I just loved the way it feels (and functionality) when I plug it in, compared to, say, plugging in a USB-C or other non-MagSafe power connections. And, I'm probably more worried about a port getting broken than the device being pulled off (my son's MBP cord actually got caught by a carpet-cleaning machine recently, and *luckily* only the cord/plug got broken, not the laptop... which did get pulled to the floor... it did destroy a couple $hundred worth of peripherals).
And, I suppose some home/office environments are different, but the likelihood of an iMac getting pulled off a desk by the cord seem pretty darn slim as well.
As to your potential Mini / iPad future, just be sure you're happy with an iPad for your mobile life. I've done that for years, but it isn't all Apple makes it up to be. First, the workflows are often different, and lots of hoops to jump. It isn't any where near as productive unless you do really simplistic computing tasks (web browsing, writing, etc.).
My mobile computing needs have dramatically dropped, so I'm getting away with it. But every time we've taken a trip and I intend on getting some stuff done, I've always failed, mostly due to just not being willing to jump the hoops, putting it off until I get back. (I get other more iPad oriented stuff done, but skip stuff I wanted to get done.)
