I don’t personally see how there exists a possibility where OSMC would implement a change here. The current situation is where we are not changing Kodi default behavior which is the preferred way to operate in most cases. Additionally I think if you were to balance the pros and cons across the entire user base to such a change I think it would weigh heavily against making this modification. I believe that currently the overwhelming majority of users are in two camps such that they are using their TV speakers and no passthrough, or else an AVR or soundbar and passthrough. The former likely is benefiting from DRC as it makes quiet dialog easier to hear, and the latter would be using passthrough in most cases so that setting would not apply.
I understand that having to know the option exists and manually make a file is a lot more to ask than just having a GUI setting. On the other hand the Kodi devs have to have some line where you don’t want to clutter the UI with niche options. I think perhaps the best thing may be to just add the topic to @Chillbo’s audio guide to increase visibility for people who are looking at tweaking their audio setup.