The budget is pretty flexible, I want to avoid compromising too much image quality and features.
That's true, I would need something with a greater range. Perhaps this one?
Panasonic AF 35-100/2,8 G X Lumix Vario Power OIS
It is a bit expensive but if it can serve the purpose of an all-round lens it should be worth it. Unless it perhaps is better to go for various lenses with fixed range? I am thinking about the price difference. I believe the best quality is achieved by fixed lenses if I am not mistaken.
There is also the:
Panasonic AF 12-60/3,5-5,6 G Lumix Vario Power OIS
and:
Panasonic AF 14-140/3,5-5,6 G Lumix Vario ASPH OIS
About the GH5 I heard it might release around summer of 2017. That will be too long of a wait.