Ok here's some more stuff I'd like to see:
Trigger/alias output not echoed in world but "what is typed" to be echoed.
A scripting function that can call an .exe file with arguments etc, this would really make this client more powerful and I don't think it really would affect the speed of it :)
You can do this indirectly if the program in question has an ActiveX interface, but in general the scripts are designed to be 'secure' from the system and not run programs that could damage things. The windows scripting host however provides for:
Dim oShell
Set oShell = WScript.CreateObject ("WSCript.shell")
oShell.run "cmd /K CD C:\ & Dir"
Set oShell = Nothing
However, I am not sure WSCript is available to mushclient (it may be a seperate component). In general allowing mushclient to have a 'run' command interface is considered a very bad idea and no direct support for it was every provided to any of the scripting languages (unless you where running a server and used WSCript).
Two solutions>
1. If the program is an ActiveX enabled one, you may be able to create an instance of it from in the script and it will close when mushclient does or the variable pointing to it is set to something other than its current contents, like in the example above. Programs like IE, Word, Excel, Paintshop Pro, etc. all support such a method.
2. Write your own ActiveX dll that executes the needed system calls to start up the program.