The 106 meters is volt drop limit, not really written in stone, 20 from centre and 12 amp even spread so working on a design current of 26 amp. I used same for radial 20 at end and rest even spread OK rest = zero.
So easy to argue 26 amp should not be used as design current.
I agree splitting the sockets into more circuits does reduce loss should a circuit fail, however main reason for circuit failure is RCD tripping so argument only valid if using RCBO.
Most houses today have three socket circuits, up, down, and kitchen. But even with kitchen removed down stairs is likely to exceed up stairs most of the time, and heath and safety wise not a good idea having a temporary extension lead up or down stairs in the event of circuit failure.
I do see a problem with lighting as you don't want lights and sockets on the same RCD in any room, however since most RCD faults are with items plugged in, having RCBO on two or three rings is not going to cost too much. However RCBO on 4 or 5 radials is starting to get expensive.
As to if kitchen ring final is really a ring final or conductors in parallel not so sure? Often only reason for 2 x 2.5 mm is can't get a 4 mm and two x 2.5mm in the centre switch. So feeding either end of a grid switch with 2.5 mm is more about getting cables in terminals than electric good practice.