[exim] Multiple dynamically-created alias files?

I want to be able to have multiple alias files in one directory. I.E. I
want any file in that directory to be treated as an alias file,
automatically, without further configuration needed when a new alias file
is added. I'd also like the names of the alias files to be reasonably
arbitrary, e.g. things like "former-user", "off-site-users", "system",
etc., so a systematic naming scheme isn't desirable.

Essentially, I want to do something like this in my alias router:

data = ${lookup{$local_part}lsearch{/exim/aliases.d/*}}

but of course a wildcard like that doesn't work, and I can't figure out a
way to do the equivalent for all the files in a specified directory.

Any suggestions? Exim 4.52, by the way.

I also fear that if I get this working it will be so resource intensive that
I will wonder why I bothered.

- Bob