How would the proposed designs be classified if they were built?

[XhanLu]

A lot of you people may be aware of the LNER 4-8-2 and 4-8-4 proposals. However, the only available letter in the system is "I", but there are two different wheel arrangements here, and "Z" for miscellaneous cannot be used, as the LNER had already resorted to using it for 0-4-2 locomotives at the time the 4-8-2 and 4-8-4 were proposed, so had they been built, how would you classify two different wheel arrangements with just one available letter?

[Atlantic 3279]

By the time of the first 4-8-2 proposals, the letter R (in the middle of a series of letters used for 8 coupled classes) was also free for re-use, following the withdrawal of all of the 0-8-2 tank engines. That does not of course prove that R would be re-used for the 4-8-2 wheel arrangement.

[XhanLu]

Well, they probably would want to use up all available letters before reusing old ones, so it would probably be I for 4-8-2 and R for 4-8-4.

[billbedford]

If they followed Doncaster practice with carriage diagrams they would have doubled an existing letter ie AA1, WW1 etc.