In reply to PPP:
I have a panasonic MFT camera and I also have the 100-400MM lens. Unfortunately it's not cheap but since I bought it I have found it a very versatile bit of kit for general photography and filming. Its excellent for portraits giving buttery bokeh, sports events, outdoor gigs, bird reserves, nature reserves.
I could go on but I hope you get the point. This lightweight lens is equivalent to a 800MM full frame lens. Check out those specs and prices to see how much of a bargain the lens actually is in comparison.
I have been giving some thought to the 35-100MM lens. After trying one in the shop and then reviewing the images that I have taken with my only two lenses, which are 12-35 and 100-400, I discovered that I either went wide or zoomed all the way in on a subject.
You could get the 100-300 lens which is cheaper and get good results as well. Personally I'd say that the 35-100 is more a close range zoom for portraits and street photography rather than wildlife stuff.
Here is a video taken outside Blackpool Tower on the Comedy Carpet at night with my 100-400 lens. I am at the far end of the Comedy Carpet to the stage.
The wide shots were with my 12-35 lens showing how far back from the stage, I was.
And here is a shot of some small birds on the beach where I walk the dog. They move incredibly fast. Taken at 400MM.
https://flic.kr/p/QPBgDy
And a portrait at 100MM.
https://flic.kr/p/TbtUWk
Personally, I'd say that the 35-100 lens would just sit on the shelf if I bought it, and it costs almost the same as the 100-400 lens.