For both technologies:
• More aspect ratio sizes (16:10, 3:2, 4:3, 21:9 flat)
• Ability to choose between matte & glossy by using a clip-on screen protector (to swap to matte)
• Front-placed OSD FW buttons. Each should be colored with a distinct color and have a distinct texture & shape. No joysticks.
• Easily accessible service menu to see how long a display has been working, along with other information.
• Large bezels for easy repairability. This would decrease backlight bleed in edge-lit LCDs as well.
• No glue in the design of the display itself for easy repairability.
• Shielding of the PCB
• External power bricks (ideally some form of linear PSUs)
• Some ability to use some form of active cooling (air or liquid) with ease
• User-adjustable impulsed mode (Bstrobing if LCD, BFI if OLED) up to 2 decimal points in terms of precision. Let the user decide on what brightness is "usable" to him. This implies that voltage boosting of ~2000 cd/m² or more ideally would be great. This encompasses VRR+Strobe implementations as well.
• Proper integer-scaling (only the AW2725QF, according to MUB/HUB is currently using integer scaling @ FHD. HD res wasn't tested)
• High density options at various sizes (21–24" QHD, 21–27" 4K, 24–32 5K/6K/8K)
• Bigger size options at good densities with aforementioned features (34–65" 4K/5K/6K/8K)
• RLA or something akin to RLA for every model.
• No refresh rate lock for custom resolutions (so one could make a custom FHD 600Hz image resolution on a 4k 240Hz OLED, if it is within bandwidth)
• Refresh rate targets which are steps of 120 Hz (240, 360, 480, 600, 720, 840, 960,...) & no OC modes (they introduce more issues than they solve)
Now, for technology specific complaints features:
LCD:
• User-programmable OD LUT, as discussed by Chief
here The only monitor manifacturer & models I've seen implement this was
Cooler Master
OLED:
• Low duty cycle BFI on any refresh rate (limited to 50:50 right now)
• Fixed VRR light flicker
• Fixed display scanout dip.
• RGB stripe (got fixed, but still not for the high refresh rate market)
This is all I can think of.