I understand the multiple perspectives on this issue (Dracthyr flying/Soar/etc.). On one hand, it would be cool to actually fly as a dragon (non-stop) in the "old world" instead of riding on a flying mount. Additionally, being able to Soar in the same way as Dragonriding (no CD, all abilities, vigor, etc.) would be awesome.
Now, flip-side (again, looking at multiple perspectives), if they did the above, anyone playing a Dracthyr would likely never use a Dragonriding mount making the system "useless" from the start since they can just "dragonride" as their player character. Personally, I would love to have full-access to the dragonriding system on my Dracthyr. However, I do understand the implications of doing so. Additionally, allowing Dracthyr to fly as the playable character versus riding a mount in "old world" content would also be very nice.