I looked into this option sometime back and here's what I found (some of this is probably redundant but I'll summarize):
1. 4th gen has the outlet in the center console, I believe there's an on/off 115V switch on the dash of Runners w/ this option. The inverter ITSELF is mounted in the cargo area behind the driver side wheel well trim, under the window.
2. As you guys have noted, the stock inverter is pretty useless for grounded plugs, and higher draw requirements. Best deal is to bypass or remove all the original inverter stuff (heck, you can still use it for charging a phone or something) and route 2 or 4 gauge from your battery (ideally a deep cycle for inverter draw) to the inverter mounted in the rear.
3. I'll be doing this over the next few months with a writeup for an OE looking appearance. A lot of inverters have a removable faceplate that holds the on/off switch and the outlets. I'll probably be mounting the inverter behind a cargo panel and extending the wires for the faceplate/outlets so I can set it flush into the rear trim panel for a clean look.
Something along these lines:
Hard mounted inverter
**Potential safety concerns:
1. Depending on the quality of the unit, I'm not sure I'd trust the stock inverter fan(s) to keep temps in a safe range. Might consider an extra fan or vent to aid in cooling - especially if the inverter is mounted in an enclosed area.
2. I'm considering installing an inverter switch that will run a relay (located near my 2nd battery) which will allow power to flow to the inverter when it's needed, and keep it under the hood when it's not.
Both those probably are overkill but certainly things to consider if running high draw items for extended time.