Does the trailer have rivets? I like to use a High performance vinyl and apply dry, so you can suck the vinyl up to the rivet. It is almost impossible to squeeze the water completly out when dealing with rivets.
To answer your question. If it is just lettering then an intermediate vinyl will work fine. it will prob. eventually pop up around the rivets, but will not hurt anything. You can mix vinyls, I do it all the time when it comes to lettering and cut vinyls. When I do a full vehicle wrap I like 3M high performance vinyl with air channels.