And, is this something most LW members would want? After all LW has long had a strongly-defended reputation as an outsider organisation -- would more involvement by "mainstream elite" take away those aspects of LW that make it what it is?

I don't see much downside in being seen as becoming more mainstream. LW isn't itself a mainstream academic organization, but it's not like we're all fundamentalist hipsters.

There also seems to be some kind of tension here - LW would like to attract more intellectual elites while at the same time MIRI is reducing efforts in the same direction MIRI 2013 strategy due to developments in the academic mainstream.

That's not actually true. MIRI is putting less effort into grassroots movement-building, but is actually putting more effort into attracting people from the academic elite. The name change was partially motivated by the need to appeal to mainstream academics, and MIRI has been fairly successful at attracting academics with little or no prior exposure to LW to their logic research workshops.