For generator charging, Mexwanderer's power supply solution is the best going. Using a timer along with the power supply can tailor your charging needs to near perfection.
For those who can't use a timer or choose not to fabricate, the newer 3 stage converters in RV's accomplish close to the same (if operating correctly).
Before I bought any charging system or upgraded, I'd measure exactly what the OEM charger is doing with the batteries you have. If the WFCO is always operating at lower voltage or pushing just a few amps, an upgrade/replacement would be indicated. A meter is essential for this and a battery monitor is even better to have.
I wouldn't discount solar entirely. If your MO is to camp at one spot for a few days and then drive all day to another, a couple of roof mounted panels could have your batteries charged while underway.
