Advice on dynamically configuring logstash 6.2 output plugin

That's unfortunate.

Any rough timeline for when that ticket is going to be done - just wondering cos it's been open for a year and I just wanna gauge whether I should wait or start on a different approach now.

I really hope the feature gets done soon as filebeat has it: https://www.elastic.co/guide/en/beats/filebeat/current/using-environ-vars.html and thought logstash would also have it.