I dont think the red and white is and ever was a viable option, especially in the old chevron design. That livery was not a Honda livery, nor was it a McLaren livery. It was a Marlboro livery and ran from 1973 to 1996 - a period of 23 years of which Honda were only a part of for five of those years. Other engines ran include TAG Porsche, Ford, Peugeot and Mercedes.
At the end of 1996 the Marlboro partnership was over and McLaren and Ron Dennis realised that gone with Marlboro was McLaren's identity (so much so that even the cars were named Marlboro Project 4) whereupon they decided that going forward they would paint the cars in their own colours. People think the silver and chrome was owned by Mercedes which was false. It was probably inspired and influenced heavily by Mercedes, but it remained McLaren's colour.
From 1997 all McLarens have been painted in their own colours with sponsors and partners adapting around it. Which is why this livery unveiled is no real surprise, although it is by now disappointingly shit. If the car still looks like this come Melbourne I'll be a bit disappointed, now was a good opportunity to rebrand a bit and maybe step away from the black and silver combo of the Mercedes era with a new design that would still retain the essence of McLaren and do the Honda partnership some justice. As you say, it's not like there are any other sponsors to get in the way. I think a deep metallic orange similar to the road car with a black and/or chrome design would look pretty striking.