I'm not OP but I work outside and use light mode. Macs are generally fairly bright as long as you aren't in direct sunlight. Solarized light mode for the win though.

Back when I did much work outside, I used a laptop that had accidental transflective characteristics. In bright sunlight, the LCD actually become quite clear monochrome, with some pixels acting as mirrors and others not, but I don't think they designed the LCD to do that.

You get an Apple product. At least, for me it was that simple. The ThinkPad I had was pretty high end, and I was using polarized glasses and even a sun shade to work at the park while the girls played. Bought a MacBook and the screen seems to crisply outshine even the sunniest days -- I haven't had to worry about outdoor use since, to my recollection.

Moving to the UK is one option. It's been cloudy for about 7 months!