Only had the scanner 1 day, so list is very short.
Back Light - off delay. If the backlight is squelch controlled, stays on for entire transmission, then have a user adjustable delay of up to maybe 2-3 seconds. This is helpful to see if the transmission is over and the scanner is back actually scanning.
LED alert, ability to offered many colors and blinking options and the LED Alert should stay on for the entire transmission.
Have not even checked to see if the x36 have colored backlighting like the x96 units. I hope so, and I hope you can keep the back light color on for the entire transmission, or at least flash the backlight color every 5 seconds.
Record/Playback - Date and timestamp of the recording with channel/system/TGID info Ability to record specific TGID's, times of day, locations.
Networking - Ability to have a wired network interface/adapter/dongle, web interface, be able to configure static IP addressing.
Audio - Ability to avoid or resume from both encrypted and scrambled audio. It seems the until will pause on the encrypted channels, but not resume after a user configured time and there does not appear to be any way to mute/resume scrambled audio.
Seems that the headphone audio and external audio are very different in level. This may be addressed when the headphone repair is performed? It apears that the volume has to be turned way up when using headphones, and down quite a bit when using a non amplified external speaker.
Do something with the recovered P25 audio, it is quite muffled, lacks high frequency content and is very hard to hear clearly compared to analog broadcasts. Note my 536HP needs the headphone repair so I have no idea if there is a problem with high frequency audio roll off due to this? My 396/996xt sound far better on recovered P25 audio. Maybe offer audio filter/EQ options in the firmware if possible?
AGC, offer an Auto AGC option. Maybe the info is buried in the manuals, but it is very unclear how to set up the AGC properly with regard to Response Time, Reference Gain and Gain Range. Again, nice features, have not had a chance to play with these or read up on them.
Trunking - Ability to configure P25 baseline decoding on a per trunked system rather than globally.
Display - Make some things disappear when stopped on a Freq/Channel/TG. Some info takes up screen real estate and may no be needed when stopped on active communications. Again, only had the 546HP 1 day, so need to play and reflect on what is being provided.
Offer different silk screened face plates and keypads so the 536HP can be turned upside down. This would also give people an option to have the main control knob on the right side again as well as be able to read the buttons.
Remote trigger turn on. For mobile installs, this also goes for the 996 units as well. Short of a master switch or relay and it appears the 536HP needs to write to the SD card on shut down, so just removing the power is not good. At least a remote shut down trigger would be good for the 536HP.
Might add more things when I have had a chance to play around a bit more.