Use of metadata in ILM configuration

Hi!

We have a logstash server that should be able to handle different types of beats. Previously we used an index pattern like this:
index => "%{[@metadata][beat]}-%{[@metadata][version]}-%{+YYYY.MM.dd}"

Now, I'm trying to enable ILM. Since different types of beats are used, my thought was to put the metadata in the ilm_ configuration fields, like this:

ilm_rollover_alias => "%{[@metadata][beat]}-%{[@metadata][version]}"
ilm_pattern => "{now/d}-000001"
ilm_policy => "%{[@metadata][beat]}-%{[@metadata][version]}"

The corresponding rollover_alias and policy (e.g. metricbeat-7.0.0) already exists.

This configuration throws errors like:

[2019-05-27T15:15:09,712][ERROR][logstash.outputs.elasticsearch] Failed to install template. {:message=>"Malformed escape pair at index 11: /_template/%{[@metadata][beat]}-%{[@metadata][version]}", :class=>"Java::JavaNet::URISyntaxException"

Is this syntax supported? Or is there any other way to set ILM configurations for multiple beats?

Same error..