You know, that is a really interesting question. A month ago I would have agreed that you would have no choice but to rewire and up your current as you ask. However, in response to another post I researched the Intellitec AESS, which was installed in his TT. Products - Energy Management - Smart energy management systems - Automatic energy select switch
What is will do is automatically shed a load like your hot water heater when something more timely comes up, say the microwave or even A/C. This would automatically eliminate your problem as the two loads would never draw simultaneously. Turns out the the 2014 National Electrical Code for RVs does not allow a 30 amp panel to have more than 5 breakers unless an AESS is installed and there are tow or more "thermostatically controlled" loads, which means A/C, hot water heater, etc.
Seems like a lot less work than running other cables, extra outlets and cords to the pedestal and it would solve your problem. FR uses them in 30 amp TTs that need 6 breakers or more in their power panel. You can get one from Amazon here Robot Check