I don't think he is good enough. Would be a perfect 4th liner who can step up, but we would be in trouble if he had to replace Kadri as a 3C. He may be able to be a passable 4th line winger though, so if the Leafs don't deem Bracco ready, they could replace a Kadri by moving Nylander into the 3C spot and have Aaltonen and Moore compete to replace Nylander's wing spot in the top 9 (with the other on the 4th line). For that matter, they could have Carcone, Korshkov, Timashov, Petan, etc. compete for it too, but I would think two of Bracco, Aaltonen or Moore would probably win. The Leafs will probably also sign a couple of grittier players (i.e. Brouwer, DSP, Acciari, Carpenter, maybe McGinn, etc.) to enter the mix. Simmonds is an option too if he comes cheap enough. Some of those guys won't be good enough to make the team, but the Marlies will have room for their veteran leadership abilities and their toughness too.
The only thing about Aaltonen is that he is going to need a strong guarantee and likely an out-clause that'll allow him to go back to Vityaz if he doesn't make the roster. He's not going to stay in the AHL.