Pointers for IPSP
To illustrate that "those should rather build an IP based network and transport CoAP as originally specified" is easy, it may be prudent to point to a (nonexisting) LWIG document that demonstrates that by the time devices only support link-local addresses and compressible ports, IPSP support is no more complex than CoAP-over-GATT (with maybe the exception that CON retransmissions over CoAP need a timer while reliable writes usually provided by the stack in simple CoAP-over-GATT case).