David .... I agree that manual control of battery charging using just the right generator-charger combination can indeed be kindof simple, very good for the batteries, and thus K.I.S.S.-like .... if and only if the charger comes from the factory with meters and knobs to do the manual adjusting.
This is especially true with respect to our camping setup. I want to charge with our little 550 VA (650 watt) four-cycle ultra quiet gas sipping Honda portable genny max'd out during initial boost charging. Using a power supply of around the size in your link but with simple adjustment knobs and meters, I'd just K.I.S.S.-set the voltage first to 14.4-14.8 volts and later to 13.6 volts - while K.I.S.S.-setting/limiting the current as high as I could so as to just barely keep the little genny's current limiter from kicking in (probably at around 30-35 amps or so).
Doing the above would permit me to experience the shortest possible recharge time using our little generator so as to not have to buy a larger portable generator or fire up the big Onan.
Here's a typical easy to use adjustable 15V, 40A (40A from the backside terminals) power supply that would be perfect for use with small portable generators for manually regulated battery charging while you sit with a cool drink or two:
https://www.amazon.com/TekPower-TP1540E-Adjustable-Switching-Digital/dp/B015QHVJP6P.S. This particular line of adjustable power supplies is also available with higher maximum current ratings.