Stock MS16 (any of them really) are pretty bad with range on a stock CM15A. After adding an antenna mod to my CM15A and a large antenna, I can use MS16a's in some places as is, but they are generally spotty. I added 18" passive antennas to each sensor and they work ok. As for weatherproof, the one I have in my woodshed has survived for several years (outside of the battery corrosion issues). The ones on the south side of my house are exposed to weather (UV/rain/etc). They last all summer without issue, but they never survive a winter. Even when weatherized (open, add silicone, close, add more silicone, add more silicone) they don't last long. The screen fails (could be freezing, could be UV, don't know). The internals do NOT like water, so once they crack, they've already been compromised.
I intended to replace them with either WiFi sensors or other protocol over the last few years. That hadn't happened. I even bought a number of MS16A's on the cheap (~$5/ea) so I could just replace them annually when they failed. That worked, but was annoying. I just replaced the fixtures on that side of the house with LED units with light sensors. I am going to keep that light on all the time (8W bulbs at night only won't cost much). I replaced the flood light with a motion sensor type that has worked great on my shop for over a year. The wood shed just had a IP67 shop light with integrated motion sensor installed and I expect it to work well on its own. The only other location I wanted to update was by my garage man door. However, there is no motion sensor that I think will work out there because the heat pump is right next to it. When it goes into defrost mode, it creates a hot plume that will trigger most motion sensors. I think I give up on that one...