The BB Hub is one of the great things that came out of BB10. It would be nice to see it in the L5. I think it would be good to make sure that concept wasn’t patented or things like that.
But as @irvinewade points out the power of Purism and L5 is open source. And, I don’t think it needs to be thought of as whether a ‘hub’ approach fits with a design philosophy. Its more about selling the UX that a device can offer. So, in addition to privacy, security, being a mobile general purpose computer it would be great marketing to see the ease of use and UX the L5 offers.
and of course it doesn’t have to be Purism that brings it to the L5. If I had development skills I would try to do it myself. Once I get my L5 that is 
I still might try, if I can find the time and learn enough about how to build apps for the L5.