I've added support for "all-in-battle-but-user" and "all-allies-but-user", though after implementing it I'm not sure I want to continue with this pattern for naming scopes.
It seems easy enough to remember though.
Will look at how "one-ally-but-user" might work.
There are a couple approaches
1. If a particular battler cannot be targeted, skip over it
2. Do not show the battler in the list of targets
3. Allow the battler to be selected, but then the action does nothing
First two are more user-friendly. Third one is just "you can select that person, but it's up to you to figure out if it works"
I don't think anything I write for the default window selection would work for yanfly's without a custom patch.