OK, let's assume what you say is true. You spent the $100k or whatever to compute a SHA1 hash collision and you can replace the bits 11011 with the bits 1010.

OK, let's assume what you say is true. You spent the $100k or whatever to compute a SHA1 hash collision and you can replace the bits 11011 with the bits 1010. How is this useful? It *MIGHT* be useful, but chances are it's not very useful, as lots of data formats are pretty lossy and a random bitflip here or there doesn't matter that much. Just because you have a SHA1 collision doesn't mean you can put any bits wherever you want and still have it be a SHA1 collision. The really hard part is being able to flip whatever bits you want(to achieve some goal, like a RCE or whatever) AND make it a SHA1 collision. This is currently very much an open problem, nobody has been able to demonstrate(that we are aware of).