Ive some methods off forcing doors here:
https://forums.alliedmods.net/showthread.php?p=1863390
Basically you have 4 options:
1) Delete them, and force areaportsls open (preferably just those associated with given doors)
2) Force them open, and disable their associated trigger_multiple by either deleting it, or by hooking its start touch and returning plugin_handled
3) take freak fortress 2's approach, and constantly send inputs to open them on a timer.
4) use stripper source to set them up, so they are how you want them before the map runs.
And yes, killing doors will generally nuke their parented models, which will reveal nodraw.
Generally best to force them open and nuke the triggers that is used to close them. Also make sure to disable the auto close.
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