Is there a way to disable headphone detection in Yosemite? What i would like to do is be able to manually switch to the internal speakers even if something is plugged in to the headphone jack. Reason being my docking station has a connector plugged in but i do not have an speakers attached (nor do i want to attach them). I think the connector is adjustable/removable but i'd really rather not mess with that.

Im thinking this is a low level hardware driver issue/feature because I have 10.10 running on my 2011 13" MBP and it still has the "Use audio port for:" option in the sound prefs. I'm wondering if maybe there is a kext I can disable or a terminal command i can use to get this option back, or otherwise allow "Internal Speakers" to be selectable even when something is connected.
That is not possible.

By design there is a mechanical switch inside the headphone jack that will automatically turn off the speakers.