I don't know for sure, Mayner, but I'm pretty sure they don't exist even if they were drawn up in outline.
Within my own family history there's no talk of it, not that this is proof it never happened, of course. As a "might-have-been", it might be expected to follow what was then the house style for new designs. Had it come into being it could have vaguely resembled a Stanier type of design, I would imagine.
What DID happen was that in early CIE times, when BR was researching the best ways to design their standard classes of steam locomotives, they wanted to take the best ideas from the LMS, LNER, SR and GWR. They extended their research to Ireland and consulted in detail with Inchicore. Family tradition has it that they took back with them some design features from the 800 class, but I've no idea which.
The 2.4.4T sounds like an excellent project for a "might-have-been" GSR / early CIE layout!
Now there's an idea.