4K is 4K no matter the subsampling.
Even in 4:2:0 you have true 4K luminance samples. In 4:4:4 you don't gain more resolution, you gain more color fidelity.
Actually, according to Kodak you need to scan film at least at 3K and downscale in order to get a good looking 2K image with good dennsity and without grain aliasing. Same with shooting digital 4K for 1080p.
Good 4 part series on the film look here:http://www.shutterangle.com/2012/cinematic-look-aspect-ratio-sensor-size...
A plan? Seriously, a plan?
If you have one, you will very well know what gear you are missing, if any.
Do you have a script, a storyboard, a shotlist? What is your location/set; have you been there; do you have a lighting plan? Is it interior/exterior? Are there practicals? Do you have a schedule?
You may not need NDs, especially if it is an interior only shoot. You may not need exposure tools other than an old-fashioned light meter, which is more than enough for consistency. And consistency is what exposure is about.
Is there a specific reason you plan to use a non-standard ratio like 2.59:1?
edit: Doh, that's been already asked.
I any case, unless you have wide vistas or clever frame utilization in your film, it's usually better to stick to a taller frame for character driven docs.
Waveforms are much more useful than histograms in that they give (partly) localized information. They are certainly not the only useful guide though. You can use a light meter or a digital spotmeter with even better local precision. False color and zebras can be very helpful too. Check this two part article for an overview of available tools: http://www.shutterangle.com/2012/exposure-tools-for-digital-video-part-1/