There was already a very long thread in the Eve Forums about the Rorq called “I missed the Fanfest Stream” that was monitored by the CSM and CCP. Ultimately the thread resulted in the Rorqual update planned for a few months back to be cancelled. The consensus was that pretty much any simple benefit to offense or defense would not be enough to convince anyone to siege it in a belt. Post-Phoebe, however, with a lower risk of dreadnought hot-drop, a simple combat buff to the Rorq could be considered, although I am still skeptical.
Another major idea was to basically change the Rorqual from being a booster ship to a miner – basically making it like a super incredible hulk. A lot of people liked it, but I don’t think it was seriously considered by CCP.
An idea, brought up by me, was adding some form of invulnerability. Apparently over a year ago, there was serious consideration given to giving the Rorqual a POS shield, but this was cancelled for technical reasons. When I put up my idea, most of the reaction to it on the thread was negative from the other posters and considered game breaking. However, I remember reading an announcement somewhere in which some Dev said that they were shelving the Rorqual update and potentially considering some sort of invulnerability that would allow the ship to be fought over. Keep in mind that while I proposed a specific idea of invulnerability, my major point did not involve details. There have been several different concepts about whether the Rorq could be reinforced, whether it would be able to exfiltrate conveniently, and exactly what the Rorq would be able to do while invulnerable, and what effects of the invulnerability on ships with the Rorqual would be (could the hulks just hide in the shield, could the Rorq and the hulks use drones in the shield, etc.)
I don’t know if they know what they’re going to do with the Rorqual. However, it is still being thought about, and it has changed from a simple matter of tweaking some numbers and buffing some stats to a major revision of how the ship will work.
EDIT: There is currently no restriction on sieging in a belt. I used to rent so deep in null that NOBODY was around. I have sieged in a belt before.