Sorry, not really. If you give me some details on exactly what you want, I'll file a feature request bug in our bug tracker for you, if you'd like that.

Hm.. it is nothing critical. Not a bug, error nor mistake. Just my idea. Just thought about it as in similar applications: All Open Office software use shared libs, Microsoft Office too.

And it could keep both Firefox and Thunderbird up to date. Now both applications update seperately, and many files (compressed, but still) are downloaded two times. The biggest files: d3dx9_43.dll, D3DCompiler_43.dll, mozjs.dll but there are many others.

You should decide if it is worth to show my sugestion..

Okay. I'll put a bug in so developers can see if this could be made somehow. We could publish it as a lite suite

Thank you for your time, have a nice weekend !

You would have to update both (all) versions at the same time to avoid inconsistencies between the DLL versions that the programs use.
It would even be more difficult if you install multiple versions of Firefox or Thunderbird for testing purposes.