I don't exactly understand your problem.
Why can't you use a system-rewrite entry in an XML catalog?

From: Abel Braaksma <abel.online@xxxxxxxxx>

Andrew Welch wrote:

Instead of using xml:base why not just create a parameter $path and
then modify all of your paths in the stylesheet to contain that
parameter, eg:

<xsl:param name="path" select="'../../'" as="xs:string"/>

I had that before. But it won't work for <xsl:import> and the likes. So I still need separate ways for separate situations in the stylesheet. In other words, the DRY (don't repeat yourself) principle cannot hold here (but who said that xslt was pragmatic in the first place, but I like to think that way).