JEM plugin for joomla contact?

Hi,
in the php of default_form.php of com_contact I found the message when I search with that I get some informations about adding custom fields and forms to joomla contact. And even in some articles a plugin to include custom fields in email.
Could this be interesting for our work? Please have a look!

[loud thinking as non-developer]
if contact could know, you're coming from JEM, there could be used a special form for easy communicating a registration for an event of non-site-users!

in the contact-model function "getContactQuery" it's loading the user plugin-group and it's firing up the onContentPrepareForm + onContentPrepareData so yes basicly it's possible to make some adjustments.

but for changing the layout you're probably better of by creating a new default_form.