That doorjamb location is fine. It is inspectable every time I enter the car, the insulation is in great condition, the wire cannot interfere with the hinges, the hole has smooth painted edges, and the wire is properly fused.
I have already stated ITT that I will source a grommet. In my experience, a piece of heater hose works better than plastic loom, if I can't find a grommet I like. I will also look a bit more for a firewall passthrough, just so the wire is hidden, but not for safety reasons. I really like this location for safety. There is no engine heat, no movement, no oil, no dirt, no salt, etc... which are all things a lot of installers will subject a wire to by using a hole low on the firewall - the clutch hole on an auto, for example, is normally a terrible spot for those reasons.
If anyone has found a nice spot which does not require slicing factory wiring looms or grommets or drilling new holes, and is high up on the firewall away from heat and contaminants, let me know.
SCT PRP FTMFW!