Keep the 65 and buy the 80 too. They are all excellent and I don't find a lot of overlap, generally. I have all the lenses and usually carry all but the 210. Even so, it all still fits in a tiny bag and is nice and light for travel, hiking, etc. enjoy and post some examples!
Due to the different frame aspect ratios between 35 and 6x7, there are multiple ways of looking at this, but I tend to consider the 43 and 65 lenses to be roughly analogous to 21 and 28 on 35 mm.
While you may well discover that you prefer other focal lengths in this format, since you do like the 21/28 combination, I would hold off the swap and shoot the 43/65 set for some time.
If I have to travel with just a single lens, though, the 65 is my choice of focal length. I am partial to 28 mm on full-frame 35 too. If you see the world in another focal length, you can probably skip the 65, excellent lens though it is.
Does that make sense? Beyond that, it's a question of priorities and finances.
Absolutely agree. For that kit, I rarely use the 150, but it does balance the kit as you say. 65 is a very fine lens and general focal length. It's just too close to the 80 to justify (i.e., afford) a fourth lens. However, if I only could have one lens it for the M7II, it would have be the 65. It's really all about your "perspective".