Once upon a time, a man called David had an idea for a way to make search better. So he hacked together a little thing and put it in Labs: http://suggesty.wmflabs.org/suggest.html. You guessed it, that turned into the completion suggester that over ten thousand users are trialling as a beta feature. So, yes, setting up some spaces in Labs to do experimental work is a great idea! :-)
The important thing for me to note is that experimental work, like any other work, should be tracked in Phabricator, prioritised by the relevant product owner (Deb in this case), and have clear deliverables. This makes sure we're not just building prototypes for the sake of it because they look awesome and make us feel good, and makes the tradeoffs involved (experimental vs A/B test) more clear.
Naming: I like Portal Labs, because the URL will almost certainly end up looking something like
portal.wmflabs.org,
portal-2.wmflabs.org, and so on, and that's already got the word labs in there. ;-)
Thanks,
Dan