Multi router 'floor' detection with OpenWRT - how to

Searched for this but surprisingly found nothing.

Two OpenWRT devices here. One as router downstairs, the other as access point upstairs.

The router is already running https://github.com/mueslo/openwrt_hass_devicetracker, the access point will follow.

The thing is, to have advanced automation Home Assistant (Hassio) should know whether a device is upstairs or downstairs.

I tried a custom source_type in the openwrt_hass_devicetracker script but HA refuses this.

2018-12-16 18:05:21 ERROR (MainThread) [homeassistant.core] Invalid service data for device_tracker.see: value is not allowed for dictionary value @ data[‘source_type’]. Got ‘router_sb1’

How to pass location data with device_tracker ánd how to use it in automations?

Same question as in https://github.com/mueslo/openwrt_hass_devicetracker/issues/16 topic:

It is possible to have the script set location_name, which overrides the home and not_home states. Would this be a good idea or will it break lots of things?

Kick before splitting question into new topic.