Here's the scenario I would shoot for. Modify to suit your needs.
Placing the inverter near the converter is a good idea.
Realize that most RV's have only one or two circuits feeding the entire unit.
Realize that the wire ran to the converter is probably not big enough to add an inverter.
1) I'd get at least a 1500 watt inverter and probably a 2k watt. (if I'm gonna go to the expense I'm gonna want to run the nuk-a-lator at least)
2) Install an auto transfer switch.
3) Replace the converter cables with larger cables (at least 2 awg).
4) Provide cooling to unit.
Check these folks out. Inverters-r-us