It should already be possible to switch lenses without changing the window layout.
1. Open the 'Lens Manager' (select 'Manage Lenses...' in the Lenses dropdown menu).
2. Select the lens you want to modify.
3. Uncheck 'Window Layout' in the 'Settings' section.
4. Click the save button to save your changes.
Now, whenever you switch to the above lens, your window layout won't change.
As Noel mentioned, lenses are a superset of screensets. By following the above instructions, you're effectively turning off screenset functionality for your lens.
Does that help?
