how to localize CAB setup DLL

We have a setup DLL that's accrued a lot of stuff over the years.
We're finally internationalizing, but I'm not sure what to do about
resources in the setup DLL.

An MUI approach doesn't work, because some of the strings are in
Install_Init, and at that point, the AppMgr has only extracted the
setup DLL to a random temporary file name in "\Windows\AppMgr\<app
name>".  I tried creating a "setup.dll.<lcid>.mui" targeted to
supposed to be in the same location as the image, but I was assuming
the system would still use the default search path), in the hope that
the AppMgr maybe had some special logic to check for an MUI for the
DLL to extract, but it didn't get pulled out for Install_Init.

We can't create our own custom installer, first because of resources,
but also because we need Windows Mobile logo certification, and that
requires using a standard CAB install.

Is there a simple approach to this that I'm missing, or is the only
option to build N copies of the setup DLL for N languages, or build
all languages into one copy with resource ID offsets and load the
correct ones at runtime (aside from ignoring localization for setup,
or rewriting the code to get rid of any need for localized strings in
Install_Init and Uninstall_Exit)?

Thank you.