Discussion, not a question. I'm just documenting here to save others the hassles. In case there's an easier way, please correct me.
We have a simple two-host farm for Remote Desktop. We're distributing the RDP file by having people log into RD Web and downloading it from there. We have two RD servers called TS02 & TS03 and another server called FS09 performing other roles of gateway, licensing, broker. All are running Win 2012 R2. After deployment but during QA check we discovered we had two issues:
1. For the computer name showing in the RD file, it was using the wrong name. It had the name of the broker instead of the farm name. We wanted to update the RD file but couldn't find this exposed in the GUI as with previous versions of Windows Server or even PS (RemoteDesktop module). To fix this we had to use the script at Change published FQDN for Server 2012 or 2012 R2 RDS Deployment (thanks TP[]!)
2. The session host servers were using the self-signed rather than wildcard cert that we had purchased and already added to the local certificate stores. We couldn't find a GUI way to select this as with previous versions of Windows Server. We had to edit the registry to get to this! We followed the instructions in the article Remote Desktop listener certificate configurations in Windows Server 2012 R2 and Windows Server 2012.