You're joking, of course. Even Boris wouldn't be daft enough to want to re-invent Mirabel.
Don't count on it. He may not intend to, but it could be the result.
Boris is working on the assumption that he can close Heathrow. The truth is that Heathrow isn't closing, hence the owners investing in new terminals. Unfortunately, proposed investment in new rwys is blocked.
Boris cannot force Heathrow to close, consequently no carrier and none of the premium business would to ill move to Boris Island. So it could very much resemble Mirabel.
DXB is in the cross roads of Euope / Mid-East / Far Aast /Oz + NZ. Boris would not be.
DXB can be justified (almost) on the hub alone. LHR or Boris cannot be.
Nor should LHR be justified "on the hub alone", it is much more than that.
LHR is at the crossroads of the
world, as are AMS, CDG and FRA of course.
Most routes via DXB, AUH and DOH are on one hell of a long "dog-leg".