It was never meant to be a sequel to ‘Commando’
This is one of the more popular stories on the internet about Die Hard. According to Stephen de Souza, the screenwriter of both Die Hard and Commando, there was a story that was broken for a Commando sequel and there was a plan to make it, separately from Die Hard. Both films had their protagonist stuck in a building. According to de Souza, 2013’s ‘Escape Plan’ is about the closest we’ll get to what the ‘Commando’ sequel was going to be about. ‘Die Hard’ was always going to be ‘Die Hard.’