Alternately, is there some existing set of practices that would help to address this?

An alternate approach is not to have lots of *.t files :-)

I tend to have a single test script for each class (sometimes based on several test modules - often based on Test::Class).

If you move 100s of *.t files into a much smaller number of files you can also see a quite respectable increase in the speed of running your tests - since you avoid the overhead of starting perl and compiling your modules.