Hey Paul,
You can't actually change a theme for a profile type but you could in the theme file code it so that it renders a unique text for users on a particular profile type. For instance, you could edit the file /components/com_easysocial/themes/wireframe/profile/default/default.php and change the codes at line 171,
[gist]
<?php if ($this->config->get('users.layout.profiletitle')) { ?>
<span>
<a href="<?php echo $user->getProfile()->getPermalink();?>" class="t-text--muted">
<i class="fa fa-shield"></i> <?php echo $user->getProfile()->get('title');?>
</a>
</span>
<?php } ?>
[/gist]
To something like this,
[gist]
<?php if ($this->config->get('users.layout.profiletitle')) { ?>
<span>
<a href="<?php echo $user->getProfile()->getPermalink();?>" class="t-text--muted">
<i class="fa fa-shield"></i>
<?php if ($user->getProfile()->id == 2) { ?>
Super Cool User
<?php } else { ?>
<?php echo $user->getProfile()->get('title');?>
<?php } ?>
</a>
</span>
<?php } ?>
[/gist]
You need to replace 2 with the correct profile id.