There arent constraints from the Unity side - there the NetApp is just like any other FC host. This is more of a question what NetApp recommends since they are putting their file system on top of the Unity LUNs They may not support using thin LUNs if they cannot deal with conditions like the Unity pool running out of space.Plus since WAFL always writes to new blocks thin LUNs could become full unless they can do regular space reclaim using SCSI unmap. Also using thin provisioning on two levels on top of each other makes management and monitoring more complicated
I have a customer who wants to know if we have any best practices for presenting  the Unity Luns to Netapp (FAS8080). They want to know if they can add thick and thin luns to it or if there any constraints.   They had originally purchased Unity 650F to use for NAS storage. Due to migration concerns the FAS8080 was used instead to migrate from another system. After further discovery they realized there was not enough disk space in the FAS8080. So rather than purchasing more disk for the FAS they requested the Unity 650F space be provisioned to the FAS8080.
Assigning Unity LUNs to Netapp