Hot end considerations for 300+ °C and greater than 1 mm nozzle size for polycarbonate I need help with finding what properties or designs I need to look for. I know that I will need these characteristics to work with the material of my choice:  


Can reach 300&nbsp;°C or up
Can handle nozzle size larger than 1&nbsp;mm
Can be used with polycarbonate filament


I plan to use it in a custom RAMPS 1.4 3D printer running the Marlin firmware, in case this changes something.
Handling a 1mm nozzle implies a desire to reduce the overall print time (otherwise why use a large nozzle), so you will need to consider not only the maximum operating temperature but also the rate at which plastic can be melted. (See also this question and one on overheating to compensate)

Using 1.75mm filament is a good start, this has a better surface area to volume ratio, but you're likely to see issues with both the heater cartridge power (so a 40W heater is probably going to help), but also the size of the melt zone and the thermal mass of the heater block.

As you need to push a reasonably large amount of heat from the cartridge to the filament, it is important to minimise the thermal resistance - so using a steel nozzle would be a disadvantage here (but since polycarbonate is abrasive, you will need to consider wear resistance as part of your trade-offs). You can get longer nozzles and larger heat blocks designed to work better in high flow applications.

Also remember that your extruder needs to work 6 times faster to achieve the same linear speed compared to a 0.4mm nozzle (with at least as much pressure), so this also might need to be upgraded (or driven a little harder).

If you can however tolerate a somewhat slower print speed, you might not need to reach 300°C  to print PC.