Not that hard, could probably take your Legion into Cyrodiil without too much suspicion, if Titus Mede II dies, then you just have to walk into the palace and sit on the chair and proclaim yourself Emperor. Being Dragonborn would give you quite a good backing, the Imperial Legions across the provinces swear loyalty to the Emperor so now you got one of the most highly trained Military forces at your command only.
So you could probably even do it with a 100 men, no one could really stop you, the Elder Council might protest, but you got a Legion at the very walls, the other Legions are on the other side of the province.