I don't think the current 'void' between 5% and 10% serves any useful purpose and it is clearly destabilizing to remove all supply or price influences on SBD within some fairly arbitrary range.
Apart from that we could quibble about exactly how things should work, like maybe the ramp should start a bit lower than 9%. But overall I agree with @blocktrades that the real debt control and safely value comes from the 10% limit, not this one, and I also agree with @timcliff that printing STEEM instead of SBD* is not useful because it just serves (all else being equal) to drive the STEEM price down, when the STEEM price being weak is the main reason the limit has ever been hit (multiple times now).
After all, even with the current 2-5% there is nothing to prevent STEEM from dropping another 50% in value after the 5% is hit and then we are right at the 10% anyway. 50% is hardly even a big move in crypto terms (we've already seen STEEM lose 90%+ of its value two or three times). Hitting 10% and risking the haircut is always in the equation, regardless of the printing rules. SBD holders should be aware of it and consider it rather than assume it won't happen.
One last point. The haircut doesn't kick in instantly it gradually phases in. So at 10% there is no haircut. At 11% there is roughly a 10% haircut, etc. There will be plenty of opportunity to see this play out and I'm sure even before 10% is reached, as it is approached there I'm sure there will be posts warning about SBD potentially becoming less-than-fully backed, and people who don't want that will have the opportunity to sell or convert their SBD (which may itself help resolve the situation). There's nothing sudden about the transition.
* An alternate rule we might consider (but I'm sure very few people are interested because everyone wants their 'free money') would be to stop printing rewards altogether when the debt ratio gets too high (rather than switching from printing SBD to printing STEEM), as this could be taken as a sign that the market is not valuing STEEM enough for it to be a good idea to continue diluting it.