Interesting question...
I suspect not as the engine ecu will have a say on the shift points... Bottom line is that the 2.6, whilst perfectly adequate, simply doesn't have the torque and power of the 3.2 and the gearbox is directed to allow for this.
The 2.2 is worse still as it needs to be worked in order to make progress. Having owned both a 3.2 and 2.2 with both gearboxes and an auto 2.6, I can attest the following...
3.2: no real difference in the way they drive except that the manual is more economical and cruises at a lower rpm due to the fifth gear. Also manual is slightly quicker.
2.2: marked difference. The auto box isn't really suited to making progress... It's quite a revvy engine and only having four gears gets tiresome. The manual gives the same advantages as in the 3.2 but allows you to make the most of the engine.
2.6: only had an auto, and whilst fine for 'normal' use, isn't really set up for anything else as the torque deficiency limits progress, hence it holding on to gears. But as it only has four, it struggles to find the right one.
I suspect that a manual 2.6 would be a better experience... With being DBW, I also suspect that the 2.6 loses something to the 2.5 in terms of driveability...
Basically if you want to get the most out of your Omega, buy a manual or the 3.0/3.2.