We at Google always check in a version of SLIME in our source control;
we build our code with precompiled support for swank,
and we debug with the matching version of SLIME.
This is the only reasonable way to be sure you can debug old versions of your servers: keep around a copy of as much of the toolchain as you need.
With this in mind, it really isn't necessary to support overly old versions of anything.
Final comment.
We at Google always check in a version of SLIME in our source control;
we build our code with precompiled support for swank,
and we debug with the matching version of SLIME.
This is the only reasonable way to be sure you can debug old versions of your servers: keep around a copy of as much of the toolchain as you need.
With this in mind, it really isn't necessary to support overly old versions of anything.