Is it possible to combine multiple forcefields to parametrise the same molecule?

In principle, the question is formulated in the header. What I mean is if it's possible to use two different `xml` files [ that hopefully have no conflicts ] to define a force-field for the same molecule? I'm interested since on top of the default `oplsaa.xml` I might have some add-ons that I would like to use without modifying the original file.