This Lowe switch was always a bit weird.
Principally because of huge changes of 2014 season. On one hand McLaren had to exclude him from development rather early, on the other he'll have nothing to do with new Mercedes car. Even if he could move earlier it was always going to be a project of a technical team put together by Brawn: Bell, Costa, Willis + aero guy from Lotus (Elliott(?)).
Which leads to a second question: how do they expect them to work together with Brawn. So Lowe is not going to be TD but someone more senior, overlooking technical side, while team is run by Wolff (business side) and Lauda - PR noise and comic relief. Where does it leave Brawn? Making strategy calls from the pitwall or what
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(let's call it "sporting side")? It's not like he hired Lowe as a "team principal".
One thing is certain, Mercedes must pay really well. Although I'm not sure what they expect to gain from that. Even if he's the greatest technical director in F1, in a short term it looks more like weakening McLaren than anything else at the moment.