Here's what I found. I'm using v7.52 of LISA.
VSEManager needs to run in a full LISA environment, you can't just copy the executable to another server.
Using Powershell you can remotely invoke VSEManager using:
Invoke-Command -ComputerName $myVSEserver -ScriptBlock $sb
where my scriptblock is the normal command line (e.g. "VSEManager.exe --registry http://myreg --vse http://myvse --username=user --password=pass --deploy c:\tempDeploy\myvs.mar"), and I copy the mar file to the VSE server filesystem before I run the invoke. So, you run the VSEManager in the context of the VSE environment, and it works.
If you are redeploying a virtual service which has already been deployed to the VSE, you must use the --redeploy switch: you need to query the VSE first to get a list of deployed virtual services, parse this and determine if the virtual service has already been deployed. If you use --redeploy on a new virtual service, it won't deploy and you will get an error. If it's a new service you must use --deploy: using --redeploy will cause an error.
I'd like to only use a "--deploy" command because I don't want to have to send a call to the VSE server just to find out if an old version of the virtual service has already been deployed - it's unnecessary because I don't care if it's already been deployed, I'm either going to deploy it or redeploy it to replace the old version anyway. Issuing a --deploy command and then trying a --redeploy command if the --deploy fails isn't right. Attempting to delete the virtual service from the VSE prior to a deploy also isn't right.
The Invoke REST API works simply by deploying a virtual service whether it has already been deployed or not, which is more efficient behaviour. It would be better if VSEManager mirrored this behaviour - is there any benefit to having separate --deploy and --redeploy commands, where only one will work in any situation? The user's intention in both cases is to deploy a virtual service to the VSE - who does it matter to if it was a new or existing service that you replaced?