I have a site that just need to sell events. There is no physical goods, so no concerns about shipping or tracking or taxes etc etc.
I want the user to be able to register his events so they appear on the various pages, and accept the payments, turn products on and off, etc.
Since these are just events, there probably doesn't even need to be a "cart" function, the classes can be purchased one by one immediately with no intermediate "cart" to hold everything.
As a bonus answer, if MODX natively isn't the best for ecommerce anything, are there any cart-like services which can integrate will within it?
why not use eventbrite and let it do it all for you?