A better example for you would probably be Mata Hari. She's a case in which being summoned in the Assassin class probably has actually made her much better than she was in life. However, she has a much lower ceiling for how much she can be improved by mana alone. Assuming Gudako is an average Master, perhaps hooked up to a homunculus she might be able to reach D ranks in a few of her statistics.
Meanwhile, some Servants will still have alright statistics even while bogged down by mana limitations, like Arturia, Cu, and Medusa.