... my MAX232-based custom interface cables ...
What commercially-available cables require RTS low and DTR high?
MAX232-based cables are apparently regarded as the cream of the
crop, which may be why you have not seen any problems.
As I noted, the Radio Shack 20-289 (the cable described in the
link), which was sold widely for amateur and scanner usage.
However, as I said (and the link noted), the circuit in that cable
is problematic for other reasons, so I'm not so concerned about that
one.
However, as I said, I have the RT Systems CT-29A, which was also very
widely sold for a number of both Icom and Yaesu radios, before
people started using USB. I bought it years ago to work with the
IC-7000. With some serial ports, it works fine with both DTR and
RTS high. However, on the Digi serial port box I'm using (another
widely sold product), the CT-29A requires RTS high and DTR low,
probably due to serial port loading (why is why some cables work on
some computers and not others).
If you don't want to do it, that's fine. I use RumTrol for saving
memories on the IC-7000, so I don't need Chirp to do it; the only
radio I use Chirp with, is the Yaesu FT-897D. However, this isn't a
pipe dream of mine; both RumTrol and Ham Radio Deluxe have seen the
need for quite some time, and it certainly wasn't me who prodded
them; my first exposure to both programs came with the feature
already there, so there must have been some demand other than my
crazy idea. Further, the feature is not hidden; it's there with
the serial port selection.
You already have a menu list with "Enable Developer Functions"; you
could always enable it there. Or, you could create an additional
item in that menu list titled "Advanced RS-232 Options".