1)
can be done by adding a custom action to the vehicle
vehicle addAction ["Get in as CP commander","scriptname.sqs"]
Then in this script you would set a boolean to true + move the
guy who has triggered the action (_this select 1) into the
normal commander position.
The extra options you could enable if the boolean is true,
and if the boolean is false you wouldn't enable the extra options.
2) The condition to to check wether he's in a vehicle or not
could look like that:
vehicle unitname == vehiclename ...(in a trigger's condition field)
or in a script:
?(vehicle unitname == vehiclename): whatever you want
The reinforces stuff i wouldn't want to explain at the mo, as
i don't know what you're already know about how to do it,
and in case you know nothing i would say: go for editing tute's
first - try/try/try - and come back with specific questions.
If you already got specific questions about it then feel free to
ask, but don't ask like above as it sounds like you need somebody to make the whole thing for you
3) There's already the CoC command engine, and then there
are also some multigroup control scripts available at the editors
depot. Further i'm also still working on my MOTAG (MOre Than A Group) where i'm using dialogue menu's to give the player control over whatever group needs to be controlled.
~S~ CD