Hi,
It seems there is a confusion in here. I don't see why SRM would not work with vCenter Appliance. You can still use the C# client with the vSphere Appliance and then you can still install your SRM plugin. It is not really a limitation of the vCenter Appliance. Though if you were mostly concerned about SRM working with the web client then unfortunately that has not been sorted out yet and we hope it will be in the future. That should not stop you though from using the vCSA.
For the list of vCSA limitations, you can visit my post at: VMware vCSA 5.5 Limitations
Thanks,
Eiad Al-Aqqad
Blog: VirtualizationTeam.com