This sounds like it would work fine. There is no limitation to the number of recordsets, updates, inserts, and DFP uploads you can apply to the page.
You could insert into tables a and b at the same time with the same form on a single page by having more than one update or insert server behavior on the page. Just make sure that you do not set a redirect for the first one on the page, you should only set the redirect for the last update or insert on the page.