This can be a question for Joomla peeps. I'm using JCE editor rather than the default small-mce. I'm attempting to personalize the formatting interface for my customers.
It is possible to method to pull "Paragraph" out of the "Format Choose" drop lower list and make up a custom stand alone button much like "Bold" or "Underline"? Something similar to this... http://cl.ly/1J1z2g1J2g2Q2X3W2R32
You'll be able to edit this content from the Format list. In JCE 1.5 visit "Groups", choose the "Editor Parameters" tab, visit the "Editor Options" area and take away the "p" (as with paragraph) in the listing of "Format Elements".
In JCE 1.5 within the JCE Wordpress plugin Manager, there's a control button "New Wordpress plugin". That can help with establishing new plug ins. In JCE 2. you will have to produce a complete installation package first.