I think we all agree here that what caused Nikon as to shine out from competition, was the 60s, 70s & 80s decades where the company concentrated in lenses that stood out and body design that where concentrated into offering a platform so that one would take the most out of his lenses...
I think it's most important if one concentrates to discuss the mistakes of the company, since this is what should prove most useful to them...
1. I still remember the awful 43-86 f3.5 lens... It was supposed to be a Nikkor lens... It damaged Nikon's reputation for for building lenses that could compete directly with the German glass at the days...
2. The F3's viewfinder info... I never understood why Nikon damped the excellent FE/FE-2 VF info (which was then used again on the FM-3/a) which allowed the user to judge EXACTLY the exposure he was going to use with respect to the camera's (excellent) metering even in complete darkness, for an inferior minimal LCD finder that lucked the difference between set and proposed by the metering exposure...
3. The renaming of the inferior E-series lenses to ...Nikkors with the introduction of the (stupid) axle driven AF system...
4. The focusing ring of the first axle driven AF lenses...
5. The axle driven AF system itself... This is strange, since Nikon was first (with the F3AF) to have AF motors in the lenses... Clearly Nikon should have delayed the introduction of the F-501 (their first axle driven AF camera) and follow Canon into using AF motors in the lens...
6. All the stupid camera designs that lasted for a decade after the FA and until the F5/F100 introduction (the design/ergonomics of which lasts up to now...)
7. The abandon of the aperture ring in the G series... Clearly the G series should have never existed... The D-lenses where as good as the AI/AI-S series on the older bodies (but the AF of course)...
8. The F-6.... A Nikon PRO body without interchangeable finders? ...that's heresy!
9. The 5 year delay as to present an FF sensor....
10. The luck of a D-800S with the introduction of the D8xx series... They left the (fabulous) D700 - the camera that established them back into a competitive company - without a replacement.... There was millions of users left without a replacement for their D700... The strange thing is that there was no investment needed as to develop the camera either, since the electronics processor and sensor was already used on the D4 (at the same production plant too)...
11. The luck of aperture ring with the new E-lenses... Very strange indeed... especially as the PC-E lenses have it and if one prefers the ergonomics of the non-aperture ring lenses, he can move the aperture ring in the "lock" position and control aperture from the camera... Additionally, the DF would be much more "complete" if the E-series lenses had an aperture ring...
12. The 8 year delay for the introduction of the E-series lenses... The interface is build in on all cameras after the D3...
13. The DF camera... No metal body? No second card slot? No 51 point AF system? ...why? It could have been the replacement of the D700 if it had the function mentioned... Especially so if one of the card slots was of the XF type and if the new E-series lenses where announced with it...
14. The naming of E-series for the new series of lenses... The E-series name is the same as the cheap line of lenses back to the eighties... It reminds of the "bad" days...
15. The confusing naming of the whole line of DSLRs... A new mistake of their stupid marketing decisions... Especially as they got it perfect for 18 continious models after the D90... It was four digits starting odd number for the APs-c models and three digit starting even number for the FF line... Clearly the D-500 should have been named D-9000 and the D-750 D-6xx (something)... then the replacement of the current D-610 should be named D-400 and thus keep the non confusing naming that was decided with the introduction of the D-3000 (and lasted for 18 continous models)... Instead, they tried to fool consumers that the D750 is a ...replacement for the ...D700 only by using a relative name and therefore messed up the perfect naming policy they where keeping for 8 years... The confusing naming is not to be taken lightly... New comers to photography, youngsters that know little about Nikons history, could clearly see what is APS-c and what is FF, as well as recognise how the line advances for build quality... Now they have a D-500 that is ...better build than both D-6xx and D-750, but it is ...APS-c (although three digit)... it's back to mess!
Can they really be back in line with their history tradition, increase sales and recover their past glory? ...easy! Here is what they should do (IMO):
1. Convert all G-series lenses to the new E-series lenses and include an (electronic) aperture ring with them... Older D-lenses still in production can wait... A renaming of the E-lenses to something else is also recommended.
2. Introduce a 16mp D-811 (or D810S) with the sensor, processor and electronics of the DF... (it will cost them nothing to do so...)
3. Rename the D-500 to D-9000... (now that it is just before introduction), It will make a clear D3xxx , D5xxx, D7xxx, D9xxx APS-c series...
4. Name the replacement of the D-610, as D-400.... Name the replacement of the D-750 as D-620... It will make a clear D4xx, D6xx, D8xx FF series...
5. Remove all colour (gold or whatever) from the lenses and just name the metal body ones to Nikkors and the plastic ones to Nikon... Nikon should keep marking on their lenses modest, just like in past...
That's all... (IMO).