I have a big messy project to build. Lots of customers, all with custom
code, all running different build versions

I already have a version.properties file that's used from within the
app. Part of my release process is to edit this with version numbers,
test build numbers etc. before building the JARs. I need to use these
same numbers in my packaging process. To avoid duplication I'm thinking
about reading the version.properties file directly into my build.xml
(with <property file="...." /> )

I'm not intending to ever update this file from within build.xml -- I
have a separate "Start making a new release" process for that.

Can anyone see any drawbacks to this idea?

Thanks.