To be honest I don't think there is the perfect solution. The problem with Gimbal heads is they are perfect for long range shooting but not the best for short range because the pivot point is around the back third of the lens - so if you set it at eye level straight on, the camera body is too high when pointing to the ground and too low when point skywards.
The ideal set up for walk around BIF is a light weight set up - say a 7DII (no grip) and a 100-400.
I personally use a carbon fibre monopod with tilt head with gives me some leah way when adjusting angles. I have a heavy set up (1DX + 200-400) but if i need to aim higher than normal I lift the lens (and monopod) and use it hand held for a minute to so (following a BIF). When I walk I throw the monopod over my shoulder (body and lens attached). Now most of my shooting is at a distance and even BIF I seem to be able to have enough angle on the tilt head to get me through.
If I am particularly going for a walk I will take a lighter body and a lighter lens (as suggested above), but my biggest problem is hand held at 400mm + is holding the shot steady enough to get a sharp shot. I personally prefer some sort of mounting platform. I must add I am under 5'10", so don't face the same challenges as the thread starter.
If anybody has the perfect solution please enlighten me.