This may involve dropping 32-bit for some things as Xcode 10 doesn't support 32-bit any more. And it may be we could drop 32-bit as target and just make new plugins to be 64-bit only.
Next we may make MacOS 10.9 the minimum, which would drop a few older Xojo and FileMaker versions. What minimum would you like to have?
Of course just going with 10.10 or 10.11 as minimum could simplify coding for us.