I found this recipe for a smbc
http://www.epicurious.com/recipes/food/views/Swiss-Meringue-Buttercream-109239

The cake im working on is a kahlua infused tiramisu filled choc cake. I plan on spraying the cake with a simple syrup of 4oz water 4oz sugar 2oz kahlua. Does this sound like a good ratio?

Then what i would like to do to the smbc and where most of my questions come from is infuse it with a tiramisu flavor. In europe and australia they have concentrate wich would be great but we dont have it here so what I was thinking is for the liquid at the end use 3fl oz of amaretto creamer and mix it with a teaspoon of instant expresso. Making sure to do this before it goes into the buttercream so that the expresso doesnt make it grainy. Do these ratios work?

The next and last question i have is, i want to add marscapone cheese to the cream. Can I use it in place of the butter or do i need to add it after. Also how much do you think I should use?