As an experienced photographer, I’m certain you would learn to work within the limitations of any camera system. OM Systems makes fine cameras and some models are rated for weather sealing.
I shoot with a Lumix G9 that I purchased used this summer. Lenses are 12-35 f/2.8 ii, 35-100 f/2.8 ii, and 25 f/1.7. Except for the 25 mm lens, everything is weather-sealed. I am very happy with this set; the glass is great and IBIS is wonderful. The kit fits in my small camera bag, and is easy to carry. I selected this over the equivalents from Olympus for slightly lower price (at the time) and more video-recording options. But it was a “close call,” as they say.
Regarding IBIS, both OM Systems and Panasonic have what I consider to be the best stabilization available. Small sensor size is a benefit here. As an example, I recently posted a photo taken at 50 mm (100 FF), hand-held at one second. Link here.
I am not aware of a weather resistance rating from Panasonic. So for your case I would suggest the OM Systems option.