As we are currently forced to select grenades with the same button as rocket lauchers, at least implement a safety mechanism to rocket launchers. Make it so you have to push another button first, before you can lauch the missile, or you have to push it at least 2-3 times or whatever - I leave it to you, but please, do something about it!
If you decided to bind one button to all nades and missiles, it's the minimum you should do to prevent unintended "accidents" and unnecessary frustration. I myself am getting tired of blowing myself up time and time again with scavended RPGs, just because I thought there is one more incendiary at my disposal and wanted to use it. By the time I realise the mistake, the rocket is being lauched at the point where you wanted to throw the nade, and you can't cancel it.
Please consider that it's impossible to confuse a rocket launcher (11 kg - from the back) with a grenade (0,4 kg, from a bandolier) in a real life scenario, even in the heat of a fight. The current mechanism makes no sense at all, it's totally illogical, conterintuitive and as such, must definitely be revised and updated.