Bawolff, I don't think the list of attendees of the current SF meeting is indicative of anything other than of the difficulty we have in talking with non-Wikimedia people; and even within Wikimedia, between WMF and non-WMF. Cf. https://www.mediawiki.org/wiki/Talk:MediaWiki_Developer_Summit_2015#Name .
As for «fairly regularly active devs for at least 5 years», we simply have no idea how many such persons there are outside our fishbowl. If, before even starting, we already exclude the iceberg of invisible people and use cases, no wonder we stay where we are. You don't need a committee to reinforce and calcify existing trends and structures.
If there is a need to expand/strengthen/diversify the committee, I'd rather look for members able to enlarge the MediaWiki contributor base in new directions. Mark mentioned some examples. Again, all this in the assumption we suffer from disunity, see my previous message.
Nemo