func_instance_parms (Help!)

[Swog]

Hello.
I've been working on a map in the Left 4 Dead 2 engine (as a campaign, which has a full storyline), and I am making an area just like one in Left 4 Dead. In order to make cars more dynamic (no shooting causes alarm, though) and have lights and sprites, I've put the car in a different map and saved it to my instance foldier in my mapsrc under sdk_content. However, I want the person to be able to select their own model. However, I've ran into a chokepoint. At Valve Developer Wiki under https://developer.valvesoftware.com/wiki/Func_instance_parms|func_instance_parms, it states only these types are allowed:


angle
angle_negative_pitch
axis
boolean
choices
color1
color255
decal
filterclass
flags
float
instance_file
instance_parm
instance_variable
integer
material
node_dest
node_id
npcclass
origin
particlesystem
pointentityclass
scene
script
scriptlist
side
sidelist
sound
sprite
string
string_instanced
studio
target_destination
target_name_or_class
target_source
vecline
vector

The prop_dynamic uses "model" (seen when SmartEdit is disabled) as a defined path. However, it is not shown in the list. Does this mean I can't use it, or do I have to use something else (like studio) or just give up implementing extra parameters?

Please?