-x is used for --regex in -F, although it's still available for -S and regex is behind --search/-s it might be confusing if you already associate with regex.

What about -Syun for
noaur

Actually a good point but instead of noaur there's a -n in query options that applies well

       -n, --native
           Restrict or filter output to packages that are found in the sync database(s).
           This is the inverse filter of --foreign.

EDIT:

Here's the entry for foreign

       -m, --foreign
           Restrict or filter output to packages that were not found in the sync
           database(s). Typically these are packages that were downloaded manually and
           installed with --upgrade.

I'm not entirely sure what the last comment means. Are you saying -n is not an option because it is already used? Any suggestions for another letter?

When a letter has been decided I want to try and implement it.

EDIT: Or are you saying that the functionality of --repo can be replaced by the -n functionality and the -a functionality replaced by --foreign ?

hi, is this still active? I would like to work on this. I am a bit new here & looking forward to contributing :)

Yup