What I do want:

• PID temperature control - for stable heating curves with minimal overshoot
• Safety shutoff - some kind of timer so if my hardware fails, the oven will switch off after a preset time. I hope to use the oven's existing timer knob for this, because it seems to be mechanical. Therefore it will still turn the oven off even if there's a blackout.
• Heat profiles for leaded solder, lead-free solder and a "dehydrate" function. This is for humidity sensitive components which need to be gently heated to drive off moisture before soldering. Surface-mount LEDs are often prone to this.
• Display of which profile is presently selected and whether a job is in progress.
• Display of "target" temperature and "current" temperature.

What I don't want:

• Connectivity. Bluetooth, IoT, none of that. It's just a distraction.
• Touchscreen. Touchscreens are unreliable, especially in a workshop setting (dirty fingers) or with very resource-constrained microcontrollers (laggy interface) I'd prefer to have no touchscreen than a poorly-implemented touch screen.
• This one might be contentious... I don't want the heat profiles to be adjustable on the oven itself. Once I have the correct profiles dialled in, I don't really want them to be editable without modifying the source code. This is partly to keep the oven as simple and "appliance-like" as possible, and partly just as a reminder to myself not to spend too much time messing with the UI of this project. All I will need is a switch to choose one of the three profiles, and a big button for "start/stop."