[raubvogel]

So, the only way to transfer all the power from engine to the wheels is to have the planet gears locked with respect to the outer gear, so engine and outer gear are rotating at the same RPM. For that to happen MG1 must also be rotating its sun gear at the same RPM. Even if we assume infinite supply of electricity to both MG1 and MG2, MG1 still is the limiting factor.

That does put a damper on my original plan (using the GS450h transmission), but that is OK: this thread is not about a project of mine but to understand the Toyota hybrid system. I think I now understand it and its limitations.