Yes. We offer this service on a case-by-case basis. Sometimes a merchant comes to us with an extension that only offers 50% of the capabilities that they need. We will gather requirements, get sign-off on expectations and provide an estimate of hours to start the project, customize the extension, test the new capabilities and deploy the solution.
Sometimes merchants come with a site that is buggy due to either poor quality extensions in their Magento site or a large number of extensions that have conflicts. We would follow the same approach as above, but in this case also fix the conflicts, test and deploy to the live site.