Things FKiSS/Unix does better:

Supports "add-on" sets by specifying multiple LZH filenames
Provides an easy way to view comments, etc.
Recursive open of LZH files (archive-in-an-archive)

More "Features" from other viewers:

Match "closest" FKiSS action and event names, a la PFK
Optionally invert sense of ghost("cell")

In no particular order...

Resize main window to contain set properly, not using magic numbers
Notice when the drawing area loses focus during a drag
Remove arbitrary limits on # of palettes ?
Handle sound("") and music("") as other viewers do
Build a real parser so that all syntax errors can be spotted reliably
Do LZH natively, and generally support it better
Editing features :)
