There must be situations where the exchange is no longer "the focus" / centre of things.
An interesting and relevant digression.
I had forgotten that BT had done a sale and leaseback of its exchanges back in 2001 (1).
Also that BT is lobbying Ofcom to change Ofcom's regulation of the traditional phone network and thus allow BT to migrate it to a fully digital service - ie. some form of VoIP service, until then under the USO, BT have to carry the cost of the copper telephony infrastructure and thus it makes business sense to maximise it's usage. Thus once again those that accuse BT of having an affinity for copper, should be redirecting their ire at Ofcom...
Going back to the exchanges, it isn't just rural exchanges being designed out; BT are currently doing this in Chelsea (3) and are expected in the coming years to have to perform a similar manoeuvre with its exchange in Holborn (4). Whilst it seems BT can design out exchanges, it tends to leave cabling very much as is and so effectively downsizes the exchange to a cabinet, with all the issues you allude to of degraded performance.
Looking ahead, I can see problems for third-party LLU and SLU operators, firstly finding rack space for their kit and secondly points-of-presence to connect to. Also given the logging requirements of the Investigatory Powers Act 2016, an exchange makes a good secure location for much of the (government funded) equipment. therefore think the decision to sell and leaseback the exchanges is going to bite in the coming years..