1) This is very simple... basically it gives you an interface to write:
so that you can browse to the filename and don't have to type in the file name manually, and don't need to write the one line of code. You could build this one yourself with the server behavior builder in about a minute.
2 and 3 are basically using the concept of designing a page as a template and alternating content through an include file that is controlled by url parameters passed to the page.
This too almost seems to simple to be considered a killer app. We could definitely recreate this functionality very quickly... The problem with 2 and 3 is that server side functionality often has to be included above the page to be effective. Anything that includes session_start() or header() manipulation including redirects would error if included in the middle of the page in the form of an include.
It seems like a structurally and functionality limiting approach to creating a site in general... and then you need to contend with the search engine friendly url issue, which I guess is easy enough with a mod-rewrite, but almost seems like an over-complication.
Wouldn't it make more sense to use a DW template, assign all of the content in the template to individual include files and then base individual pages off that template? It is basically the reverse of the above technique, where the MX includes concept has a static page and the content is controlled by includes, it would use includes for the page structure and control content on the individual pages.
This seems to me to be the more functionally and architecturally sound technique that shares the advantages and eliminates the disadvantages... anyone want to correct me here? I might be missing something.
The bottom line is that recreating this extension would be relatively easy. My problem with it is that I don't think it encourages a fundamentally sound site and page structure, and I don't like leading people down the wrong path... either way you are creating a new page for each content set. Either way you can change your entire design by editing a single page.
Nextensio is a data grid. We are investigating this as a potential addition to our toolset, and it is very likely to be produced sometime next year.