I'm taking into great account the last 2 posts, about the guide and above all the clear tips for starting with the right step. I like the idea to "study" com_banners on the admin basis and about the AkoComment I think that I'll have a glimpe at that but I don't think to just rewrite the system...

My idea is to project a new comment system with some features, well known in AkoComment, inside it. So starting from a stable simple but complete version...
And about the spam comment risk, personally I don't like the image feature, it's difficult to read, it isn't an accessibility option, etc. IMHO it is important to have a wall against the spam but avoiding this confusing and ugly (graphicaly too) way of prevention. I have a revolutionary idea (but very simple) for that, never used before

but I am wondering if it is efficient or not...

(another problem, so).
About the DB, I'd like to maintain the same one but for hardening the system I need at least another field for ID user... I think that an "upgrade" way such as a converter package should be necessary
But at the moment I need to have well in mind my first step:
study the plugins guide
study the com_banners (admin)
find out a simple plugin in 1.1 for studing, too (any tip?)
study the com_content for editing/pubblishing rights
And about the request parameters, if I well understand these are the most important for my project:
JRequest :: getVar( 'task' )
JTemplate for patTemplates
JText for internationalisation
... stop?