I think you're misunderstanding what Odyssey has told you. You do not need to override the economy mode, as the higher charging voltages are only necessary when the battery has been deeply discharged. This wouldn't include regular starting and usage, but more like extended winching times where you actually drain the battery down in one go. In that type of scenario, where you actually drained the battery, you shouldn't rely on your alternator anyway and should be using an actual high amperage battery charger (the literature states charging at a 40 amp minimum at 14.7 volts).
"To fully charge a 31-PC2150 and 31-800 battery that is routinely discharged deeply,a minimum of 40 amps are required with charger voltage within the range of 14.1V
to 14.7V. It is imperative not to exceed 15.0V as this will cause the pressure valves
to open and out-gas hydrogen, oxygen and water from inside the battery. This will
shorten the life of the battery and cause premature failure. Some portable chargers
exceed 15.0V, especially two-wheel garage chargers, so charging voltages should
be verified by measuring the charging voltage during the time when the charging
amperage is reducing from full output. The deep cycle charging voltage must be
within 14.1V minimum to 14.7V maximum."
Regular use the reduce voltage provided during economy mode is going to be fine since the maintenance charge voltage should be around 13.5-13.8 volts.
The factory setup is going to handle keeping an AGM battery like the Odyssey charged OK. Not perfectly, but OK. Really this is true even with flooded cell batteries, you need to put it on a charger to really properly charge it all the way. If you're that worried about it then what you'd really need to do is have someone reprogram the charging patterns to suit the charging voltages and state of charge levels to match AGM's vs flooded cell.
But the differences between the two are very slight. Flooded 12v battery is fully charged at 12.73 volts open circuit, while an AGM is 12.84 volts at 77 F. Just over a tenth of a volt, which isn't enough that I'd worry about it personally. And the float voltages are only slightly higher for AGM vs flooded, by about 0.3 volts (13.8v for AGM vs 13.5v for flooded), while the charging voltage is lower for AGM by about 0.3 volts (14.7v for AGM vs 15v for flooded). The differences are small enough that even if it does reduce the life of the AGM, it won't be by very much since there are far more variables at play in a vehicle's power system that will have a greater affect on the life of the battery. And actually the limit of 15v is really if the temperature is moderate, if it's below freezing then it can get up that high safely since really it's the heating issues that are the problem rather than the actual voltage level (meaning you can charge them at higher and higher voltages the colder the ambient temperature and temperature of the battery are).
I don't feel it's worth the trouble and expense to reprogram the computer, and Odyssey and Optima wouldn't be selling their batteries to anyone that buy them if the typical vehicle charging system was going to ruin them or cause their life to be drastically reduced. Just buy the battery, and if you've had to do any winching or running loads off it without the engine running, then when you get home put it on a charger that is setup to properly charge AGM batteries to restore it's state of charge to a properly full amount.
