Not aware of any scheme and if so, anyone with so much as a beer belly will be claiming special treatment and trying to queue jump.
An immgration visit need not be taxing, I find I rarely do anything and the wife does all the running around.
Many offices have outdoor waiting areas environments since covid, that is the bit I hate.
But if you clearly having difficulties, ie using sticks, a chair or a walking frame etc. they will help you, they are not bad people.
I