to go back on the original question ...
you have some constraints here with some parts carrying not only a long lead time in production but also along leadtime to develop.
there are parts you need to finalise -have a design freeze- quite early in the project to allow other departments to do their work .
So you may be sure able to change minor details of the tub later in the year but a switch of short to longwheelbase will not be possible without major compromise.
So I´d guess your Tubs general shape and layout is done now and the guys will start to produce the molds s for it.Clever guys will integrate changeable inserts into the mold which opens the door for detail design changes without affecting the prototype production and allow for aa seamless build phase even when some departments struggle to find an end to some discussions.
But in the end you need to be ready with the first tub end of September .In other words the talk about switching recources towards the next year now is total blabla
it´s necessary to start much earlier ,say May or early June to decide on concepts
and even if you have 2 or three possible directions still going early on I´m sure in july you are so far advanced that it is only onne direction yoiu are pursuing.
the one thing you might stop or not stop early is the aero kit for Spa/Monza .Those chaps who struggled to produce a competitive machine out of the box will of course have delayed the development for that or split the development in two (taking interims solution to Canada)and push forward with new parts to gain some speed ..this is obviously slicing off chunks of development time in a crucial phase for next years contender -especially in aero .with only one tunnel ,you cannot run two cars at once.(Can you?).that would make for a nice idea under RRA rules
Having a tunnel with two test sections and you can switch the flow from one to the other via opening gates ....this could reduce down time due to thwe tunnel speeding up and slowing down and would ebable you to work on this and next years car at the same time..
But in reality you need to start when it´s time to start.Planning is derived from the date you need the car at the very latest...and you take it from there.To me it´s amazing that a team like Mercedes is not finished with the car in time.You got a clear understanding of what takes how long to design and manufacture ,you got ideally a PLM tool with project management and requirements management,compliancecheck,BOM,Change management and management of suppliers. bearing in mind you have build formula 1 cars since 2000 in that facility...
check Honda introduced plm by Siemens only in 2006 to switch to Dassault in 2010..
http://www.plm.automation.siemens.com/e ... nent=30477