My two cents worth!

Michael's "legitimate" front was the Elephant in the room
I reckon, nobody would be willing to resurface all the charges against Michael raised in the dismally failed Senate hearings

No doubt Roth was still a threat but not an immediate one He needed to be eliminated but not at any cost and the airport was not the only chance

Tom visited Pentangeli who was living in an army barracks with the FBI guys so they could get to Roth later

I reckon, Michael would not sacrifice his men especially his top men He selects his top men so that he can do the job successfully and get away with it

I still reckon killing Roth need not have been a suicide mission

What is this about Rocco, with only one good leg, bum leg
If he had an escape plan, he need not have to outrun the feds and their bullets His running is what got him killed