This is covered by the BS5839-1, I am awaiting my new copy as a new version came out end of last year and I have to design an installation myself, I will thus hold back on quoting the exact regulation.
It is hard to comment from a plan of the building tbh but their is nothing wrong with a frame fixture and if a new build the cables can often be hidden in the hollow frames or by using a neutral colour to contrast the frame if trunking is needed - black trunking does sit well on silver without standing out too much.
I have fitted the CP's away from the doors before but each situation is unique and also it depends on the building, its use etc, sometimes a call point is not even required believe it or not, you find this is pubs where the call point is often located behind the bar and not next to the doors where they are often accidentally or deliberately smashed.
I would suggest you get yourself a copy of the BS5839-1 and 5839-6 if you are actively designing and installing, after Glenfell I have found the reluctance from building control, fire services and other bodies to give written guidance or opinions, this leaves it on to you to be fully converse with the BS5839 and document anything that is verbally agreed with BC or the local Fire Services.