I'm about to launch my product. I'm currently preparing the website, documentation, e-commerce integration and so on.
It lacks features that will be added in the next few months that will allow it to take full advantage of the product potential (mainly generate alternate valuable output in the form of reports, which only some users would require). These new versions will be easily upated and without need to pay again (for major versions).
My question is, how to market this MVP for maximizing sales in this early stage and minimize users "waiting" for an "1.2" post-MVP version?
I'm a little confused. From your question it sounds like you want to market an application that currently does not generate valuable output, but may, someday.
If that's the case then it's not really a minimally viable product, launch when the product can actually do something not before.
Otherwise, do what the cool kids do: Just launch now and iterate often and fast. Have a blog with the latest new feature (hopefully you are posting at least weekly).
I think you have a range of options:
If the 1.2 features are the ones people will bite on then your MVP is V1.2 and before that your real value is the feedback and bug fixes to get the product over the initial pain points.
If you can, forego the early income stream in exchange for the feedback and evangilism of the early adopotrs. Show them what it will cost them if they hold out and say "but if you get it now it will remain free to you through to V2".
This will let you
A defition of a MVP would be that it's not always a product itself, but an announcement of some of the features of a future product. This can be a video, screen-shots, limited demo of some primary version with limited set of fetures only.
This phase is being used to get feedback from your initial base of customers, i.e. early adopters that might or might not become real paying customers later. So, make some presentation of your product and spread the word through forums, social media and blogs to relevant users and ask for their comments about what they see at the moment and what would like to see in the future versions. Then evaluate the feedback, say NO to most of the feature requests at first, and then list them by priority and implement one by one and notify your user base about the advancement.
How to create the user base? Ask for their email via simple subscribe form, ask them to leave comments on your blog or forum and notify them via email about replies you leave later, if it's possible, if not, go ahead and spread the word again about update this time, as you did at the begining.