That's a plausible plan, anyway. I'm guessing that the current plan might also involve taking over the rest of the magical world, and then the muggle world, a goal that might not have been originally desired or seen immediately feasible, but which acting as Harry could facilitate. Ch. 20 provides a possible motive (prevention of technological existential risks; Riddle is rational enough to notice that comfortable immortality requires as a necessary condition that the world is not destroyed):

"Those fool Muggles will kill us all someday!" Professor Quirrell's voice had grown louder. "They will end it! End all of it!"

Harry was feeling a bit lost here. "What are we talking about here, nuclear weapons?"

"Yes, nuclear weapons!" Professor Quirrell was almost shouting now. "Even He-Who-Must-Not-Be-Named never used those, perhaps because he didn't want to rule over a heap of ash! They never should have been made! And it will only get worse with time!" Professor Quirrell was standing up straight instead of leaning on his desk. "There are gates you do not open, there are seals you do not breach! The fools who can't resist meddling are killed by the lesser perils early on, and the survivors all know that there are secrets you do not share with anyone who lacks the intelligence and the discipline to discover them for themselves! Every powerful wizard knows that! Even the most terrible Dark Wizards know that! And those idiot Muggles can't seem to figure it out! The eager little fools who discovered the secret of nuclear weapons didn't keep it to themselves, they told their fool politicians and now we must live under the constant threat of annihilation!"