[fragmede]

Unfortunately, that's a "could an omipotent god create a boulder so heavy he can't move it" level of "logic puzzle" and does your argument no favors.

[Borealid]

It's quite the opposite. Converting to words like yours, the argument is "could a powerful but not omnipotent god make themself more powerful", and the answer is "probably".

If the god cannot grant themself powers they're not very powerful at all, are they?