Coming to this exceptionally late (and in fact getting myself a new log in as an old email had lapsed some years back, so I could comment)...
First, I wanted to suggest two possibly-too-obvious 'types' with Barton Wright (of the LYR)'s finger prints all over them (I don't think these have been mentioned in this thread?):
His 0-6-2T design (initially a rebuild from a Jenkins 0-6-0 tender loco)
... which ended up being effectively a 'standard' Kitson design and versions thereof with the same curved tanks and bunker emerging on the TVR, LDECR and H&B...
I'll paste in a link to the LDECR and HBR types
LNER Encyclopedia: The LNER Kitson N6 (GCR Class A) 0-6-2T Locomotives
LNER Encyclopedia: The LNER Kitson N11 (HBR Class F1) 0-6-2T Locomotives
Barton wright also rebuilt some Jenkins 0-6-0s as 0-6-0ST.
And then there's also what happened to his own 0-6-0s when they were rebuilt as 0-6-0STs by Aspinall...
...which it has been commented, is quite similar to the Sacre MSLR 0-6-0s rebuilt by Robinson as mixed-traffic dual-braked tanks
These are not that obscure, and I don't think it's impossible to see them as 'generic' types that aren't 'owned' by either Kitson or the parent railways... particularly if your railway is anywhere north of Bristol and south of Carnforth.
...It's entire possible, I guess to mix them up and have a tender type with 0-6-0ST and 0-6-2T (and if you want 0-6-2ST) variants, all working alongside each other, and starting out as three (or four) members of the same class; and if you really want you can have a 4'6" or thereabouts coal engine 0-6-0 type, and a 5'3" or thereabouts mixed traffic 0-6-0 type, begetting a number of tank 'children' of various combinations of features. (I believe I'm right in saying that the DX Goods lurks behind all these locos as an indirect influence, but can't evidence that right now).
(This all came about because I saw a picture of an 0-6-2T at Lancaster Castle station, and thought 'what's a GCR loco doing there?' before I realised my error.