You might consider renumbering the figures, e.g., Figure 1A and Figure 1B. You can add a brief description of the drawings:
Figure 1A is a .... .
Figure 1B is a ... of the elements of Figure 1A in greater detail.
Figures 1A and 1B are sometimes referred to collectively as "Figure 1".
The last line is an attempt to avoid editing every reference to Figure 1 in the specification.
This approach has the advantage of filing marked up copies of the figures, making clear exactly which Figure 1 is which.
Food for thought?
To Jim: But doesn't the qualifier "Figures 1A and 1B are sometimes referred to collectively as "Figure 1".
" undo that clarity? If you amend the captions to "Fig. 1A" and "Fig. 1B", but do not amend references within the rest of the spec, I'm left guessing as to which fig to turn to when I read "Fig. 1".
To OP: Let's call Fig. 1(1) the less detailed drawing and Fig. 1(2) the more detailed drawing. Is Fig. 1(1) a true subset of Fig. 1(2), that is, is every feature in Fig. 1(1) also in Fig. 1(2) and are the call out numbers the same? Was including Fig. 1(1) and Fig. 1(2) strictly an error, or were they intended to illustrate two embodiments?