Android

Larger, swappable battery. Squeeze for assistant

Ability to use the screen as a display through the USB port so I can debug a lot of my systems at home without needing to carry a monitor around.

I loved the IR Blaster on my old Galaxy S4, was really fun to mess with the TV's in public places with it sometimes and was also pretty useful at home as well!

I'm on a Fold 4 now and I do love the novelty/oddity aspect of having a folding tablet.

But I would love to see the return of IR blasters on most phones and sliding phones for physical keyboards.

Phone upgrades.
Battery.. Non lithuim. Flexible and new. []
Flexible screen. Wrist strap or just flexible. []
Fitness/health capabilities. []
Usb 3.1 reversible.. Proper specs [x]
Wireless charging. Using new WiFi microwave to charge phone without mat. Wattup []
Better nfc/Google pay [x]
Smaller screen oled,s than 5.5 []
Better speakers none conduction or ceramic
Encryption []
Bezelless. Screen to screen hole cut out. 2018 []
Solar panel in screen. Sapphire glass. Smudge and germ

This list was created a few years ago.

Some things have been implemented but not all.

Really would love a dedicated camera button that acts as a soft shutter release. Or a button in that position that's programmable.

Slide out controller, like the Xperia Play. I've gotten super into (at least the idea of) SBC handheld gaming, and there's just nothing quite like the Xperia Play now. Sure, there's bluetooth controllers, but I'm not a big fan of bluetooth, and the majority of the bluetooth controllers make portability a pain rather than it being a sleek package.

Modular everything. I really wanted Project Ara to come to market.

Hackability

Native Bluetooth GPS support. I do mapping for OpenStreetMap a lot and the built in GPS modules are just too bad for that. Currently I have to use an app to get my Bluetooth GPS connected. But sometimes this app fails and the built in GPS takes over and ruins my logs.

I enjoyed the squeeze to activate assistant on Pixel 2 XL..just felt right. I even configured it to activate flashlight when I needed a quick light.

Headphone jack, apparently..

Today my wish is for an internal pihole instance running on the device.

Does the alert slider counts as a niche feature? Very few brands provides this.

I've had 3 Motorola's where the charge port stopped working just past warranty. Now I always look for wireless charging.

I will never buy a phone that doesn't have GrapheneOS, so that limits me to Pixels.

This is going to be such a stretch and I doubt this would ever happen, but if you could get a decently sized camera sensor on the back of a phone and a mirror less style lens mount...I would sell my DLSR in a heartbeat.

It's the rear fingerprint reader for me, I use the pulldown action constantly. That and stereo front-facing speakers.

Foldable display - They are still way too expensive!

Metal case - I just loved the heavy Samsung Omnia 7 metal case. It made it unbreakable and grippy!

Removable dual display like in LG G8x, V60 etc. When you need it you can have a beast of a phone with 2 screen or a slim normal flagship.

IR blaster

duck duck go tracker blocking that doesn't use vpn technology

Officially supported rooting! Makes this less complicated.

One without a damn camera, I swear to God most of the price goes into having "quality cameras" I never end up using.

A swappable battery. I could buy a few batteries and never be out of power. I could replace the battery on an older phone without pretty much having to replace the phone itself.