Facebook – Change the start point of Facebook Page Ads

Currently, Facebook doesn't support it from standard interface. But, Facebook can merge your page with app if you contact them. Facebook once accepted my request few years ago.

240 isn't a big number. So, its likely that they wouldn't listen. But, go try.. specially when your company has big offline profile.

In case you're out of luck, post the link of app on page with catchy words many times. It can draw attention of existing fans. And, if they are really fan, they'd like your app for sure.

Put link of app on welcome tab of page, too. Its for your existing ad campaigns.

I came across an article that discusses pretty much the exact process that I described above, so it seems this is feasible. The article does differ a bit from the steps I mentioned in the question. Instead of renaming B to C, it suggests renaming the profile A to page B before you convert it to a page, and then merge the two pages together. Not entirely sure how that would work exactly.

In absence of other answers or feedback, I will just go ahead and make this the answer unless something better comes a long.