Your first suggestion is correct - there should not be two different views (of any type) with the same letter on any one drawing.
See the quote below from ASME Y14.3-2003
1.7.3 Identifying Removed Views. To relate the viewing
plane or cutting plane to its removed view, capital
letters such as A, B, C, etc., are placed near each arrowhead.
The corresponding removed views are identified
as VIEW A-A, VIEW B-B, VIEW C-C, etc. View letters
should be used in alphabetical order excluding I, O, Q,
S, X, and Z. When the alphabet is exhausted, additional
removed views shall be identified by double letters in
alphabetical order, as in AA-AA, AB-AB, AC-AC, etc.
This applies to all "Removed Views", of any type.
I, O, Q, S, X, and Z are all excluded due to their visual similarity to 1, 0, 0, 5, [blank that needs filling in], and 2, respectively.