BSc: double thesis or thesis with multiple topics?
If you can make one good story about the combination of the two, that's what could make your thesis outstanding. But it's also going to be a lot more work, and if it doesn't work out, you just wasted a lot of time.

If you're not convinced you can and really want to pull this, go and ditch one of the two subjects. It's a lot less hassle for both you and your prof, you'll get a good grade, and that's it.

As was mentioned in the comments, it's already published, so there is no need to publish it again, and in a thesis, which so few people will read ever again.