You've got to think about practicalities as well. If it followed the 363 route down Wood Vale and into Forest Hill it would have to terminate somewhere convenient, somewhere either quiet or with lots of space, or preferably both. There's nowhere suitable in FH, with relatively narrow roads and bottleneck-tastic traffic. A London road terminus would be a nightmare. Also, it needs to turn round, and you couldn't do this without going down Dartmouth Road at least as far as Sydenham or round the Catford one way system, whereas the junction of Wood Vale and FH Road has been redesigned for the purpose.

Also, a doubling of bus traffic down Wood Vale or HO Road mightn't go down too well with the residents. Though the extra wear on the road and facing buildings may uncover some remnant of the Moore Park Tavern.

I'm less familiar with the road layout in the 'SE4 borders' bit of SE23, but it doesn't look that promising there either.

I'd certainly use a bus that began at the Wetherspoon's, say, and then basically ran like the 363 (particularly on Sundays when I have to go into town and the BLOODY TRAINS ARE OFF), but I'm not sure how you'd do it.