Sounds like you would have to consider using the security features of vr's and NAT on the router, to be specific double NAT. If you could add the same subnet to each vlan, then how do you suppose arp would respond? All traffic would still be switched locally. This is the article that describes that feature. it will be interesting to see how that feature is implemented in your environment if not using double NAT. the users would have to send traffic to a diferent destination address which the router would NAt to the subnet and vice versa.
https://kb.juniper.net/InfoCenter/index?page=content&id=KB21286&smlogin=true&actp=search