Automatically block pull request merge if one person rejects it

Hi, my name is Miguel Ángel Romero Lluch from Spain and I am working for the newspaper company Vocento as a Technical Leader developer.
We have been successfully working with JIRA over the years and we have just adquired a license and setup an offline BitBucket solution in our Vocento servers.
I am also a freelance developer hosting an open source Firefox Extension in BitBucket.

In our first tests we are finding great features and we are happy with BitBucket. We have found one feature which is lacking that we would really need for the management of Pull Requests to fit our development Team needs at Vocento.

When we setup merging options of Pull Requests, we can currently setup 2 things:
1. Number of reviewers who need to approve the Pull request.
2. Requirement of all reviewers to approve the PR.

We would need a third feature:
3. Do not enable Merging of Pull Request, inmediately after 1 person rejects the Pull Request, even if others accepted the Pull Request before, or even if someone accepts it later.
Example:

• 2 Revievers Accept the PR.
• Third reviewer Rejects the PR. ---> Merge is automatically disabled.
• Fourth reviewer Accepts the PR but he wont be able to merge.

In this case Merge will not be possible until the Third reviewer accepts it, or a new Pull Request is sent with the proper fix.

The use case for this would be that some developers has reviewed the Pull request, but one of them detected something that the others did not.

I think this core feature would be awesome and it is something critical for us since we could avoid Merging Pull Requests even in the case of someone who has spotted something wrong.

Thanks.