I kind of wish there was a way to remove a terminal and go back to the standard leased gates without having to remove every flight and add it back. I know I'm probably the only one who has thought of this or even wants it to be a feature.
Another idea would be to lease more gates instead of expanding a terminal as this would be quicker due to less capital being required. Then maybe you could transfer flights using the terminal to leased gates and then demolish the terminal. Idk, this probably seems very stupid and I'll get responses like "wHy DiD yOu BuiLd ThE tErMiNaL iN tHe FiRsT pLaCe ThEn"