Temporarily Replace Skylight Window with Plexiglass

Hello,
I have a skylight in my room and was thinking about temporarily replacing the glass with a plexiglass sheet in order to vent a portable AC unit out the window through a hole cut in the plexiglass, and running flexible duct up to the glass, which is about 8 ft off the ground, then terminating the duct at a 90 degree elbow in order to keep water out. The skylight dimensions are 40" x 40".The room is in the middle of an apartment. 3 walls are interior, while the exterior wall is shared with the building next door. No other window exists in the room.
The skylight glass is a dome, and is easily removable by lifting up. Skylight glass is not hinged.
Would there be any issue with this scenario? I would mount the plexiglass to the current window frame and use sealant to keep out water, then in the colder months remove the plexiglass and put the window back in place.