Lighthack with 6 encoders and 6 LCD - need advice

I don't know of an arduino that could support 6 lcd displays and the encoders as well. You may have to do one per display or maybe two displays per arduino. They take quite a few pins. There are some i2c backpacks you can get for the 2X20 and 2X16 displays that reduce the number of pins necessary. I've done 4 encoders with 5 pages and a 2X40 or 4X40 display on one Teensy 3.5 all based on the light hack code

Is it possible to do one long display that stretches across the top of six encoders?

Yes but I don't think the 40 character display will have enough room for 6 encoder labels and you will have to use small encoder caps to bring them closer together. The best I've seen is someone used a 2x20 display and a 2X40 display side by side with 6 encoders. I'm not sure what they did controller wise but would expect them to have one arduino for each display and it's encoders.

I'm not going to use small encoder caps.

I'd prefer a longer display, but if a 40 character display is the longest possible, I can use that with lines pointing to the proper encoders. The original Eos had an array of encoders that extended past their display.

40 characters is enough for the parameters I want:
1234567890123456789012345678901234567890
INTENSITY RED GREEN BLUE WHITE AMBER
INTENSITY PAN TILT CYAN MAGENTA YELLOW
INTENSITY PAN TILT IRIS EDGE ZOOM

Can you please provide me with model numbers or links for the 2x40 and 4x40 displays you've successfully used?

www.amazon.com/.../ref=oh_aui_detailpage_o09_s00
focuslcds.com/.../40x4-stn-character-lcd-c404albsbsw6wn55pab

I've also used the 2x20 displays from adafruit both with and without the i2c backpack.

You can buy one from china, needs some time to deliver, but very cheap:
www.buydisplay.com/.../character-display