Biztalk Deployment Without Downtime

Hi, I have a query regarding biztalk deployment. We have biztalk 2010 environment where a common biztalk solution is present where all common schema, pipeline and etc are deployment. We have other around 20 biztalk application which is dependent on common biztalk solution. Now there a change in existing dll (schema dll) which is already present in common biztalk application.  And we need to deployment of 2 new biztalk appliation which is again dependent on biztalk common application. My question here is how can we do deployment in this scenario without taking any downtime. As other 20 biztalk application is dependent on biztalk common solution so while modify resources in common biztalk solution, it ask to undeploy dependent 20 application. 
Thanks in advance.Regards,Lalita