I love my H9 and have a T1m aux switcher which gives me three more switches. It works like a charm, I have it programmed to; decrease preset, tuner tap. With the two buttons on the H9 this covers all my live functional use. One problem, I have to switch presets with one button then press the "activate" button to activate it. It auto loads when in preset mode using the encoder wheel but if using switches the activate button is used to engage the new preset. I wish there was a toggle to change switch preset changes to auto load as soon as you stop scrolling. It's too clunky in the middle of a tune to push two buttons to change presets.
In the next release of H9 software, we are going to add Load Next and Load Previous functions that can be used to go to the next (or previous) preset and load it automatically. This is slightly different than what you described, but hopefully, it will be an improvement for you nonetheless.