It would be useful to have built in “Channels” as an entity having their own attributes) and allowing Features / Initiatives / Releases to be related to one / many channels.
The way we organise AHA is to have our products that we want to deliver accross different channel (Web / Mobile / Retail etc) - I am kind of making this work with custom fields but would be great to have a channels entity.
We see "channels" as macro information about a feature. Now, some customers define their products by channel (e.g. iOS app) so they organize their products this way. Others use custom fields or initiatives as you are doing. Some even use tags. I do not see us adding a default field for "channel" though as it definitely is not relevant for all of our customers and we need to do our best to only add default entities for what is fundamental for most customers. I hope that makes sense.