If I missed Mincha because of a late bus, but in a situation in which I could have chosen in time to simply cancel my intended trip and go Daven Mincha at home, may I still daven Maariv and repeat the Shemonei Esrei to make up for the missed Mincha?

If one missed out on Mincha by mistake he can compensate for that by davening Maariv Amidah twice, if one skips Mincha intentionally with no valid reason he does not have that privilege and he lost that Mincha. [Shulchan Aruch OC 108] I think that a person who decides consciously to skip Mincha for a bus ride qualifies an intentional skip, however if he did not know that he can daven on the bus seated and that’s the reason for missing out on Mincha, this case goes back to be a mistake [in Halacha] and can daven Maariv Amidah twice.