No official view here, because 1) it's only my opinion based on knowing how various types of systems are tuned and function, and 2) there cannot be an official (or any other) position on a possible problem that has not been described.
Absolutely correct on the goal, and seamlessly handled by Speeduino tables. As already mentioned, with Speeduino you do this with your throttle, placing the engine operation into specific areas of the tables, providing different fueling, ignition timing, AFR targets, etc.
Your "crazy Latvian guy" tells how he changed fueling and timing, without saying why he needed that capability beyond they typical capabilities of modern systems. Again, if you could outline the reason(s) why this is not possible on Speeduino in standard form, then we could analyze why and how it could be resolved.
Again, he does not say why, but only how he had to do it with a different older system. Speeduino does not have the limitations of EEPROM chips nor require an EEPROM extender, nor require switching them, nor using an emulator to tune. As shown in the Wiki, a Speeduino table will respond to any tuned conditions with the proper timing and fuel with software-configured tables. Extend or shrink them as you like and is appropriate for the engine setup from idle to nearly unlimited boost - configure it, tune it, and it will do what you tell it to do.
It needs more fuel and less timing at 150kPa? No problem. Even more and less for 200 or 600 kPa? Again, no problem, assuming you have the right parts. Or, much leaner and far more timing at 50 kPa for economy? Well, you know the answer, all in one tune. Again (again), if you have a special issue or consideration as already mentioned, tell us exactly what that is. Else, this system should work fine for controlling your turbocharged G10 for maximum performance, both in power and in economy, in 'standard' form. Comparing how his system and this system work is a poor use of time and effort. Learn this system and go do it. Or, use his system and do it his way. No problem. Your choice.