That is the big point, if they have to move things about in order to put in a movable steering rack then it'll need a new chassis - a major expense that not many even think about. I would have thought the design of the rack is relatively straight forward, but you are right if the chassis needs(with the expense involved) to be altered not many will do it.
Mclaren in 2018 knew early on in the year that they needed a new chassis, to lengthen the space between the front wheels and the sidepods(to clean up the wake from the front wheels etc), and they didn't produce a new chassis until the following year. It'll cost millions to do for relatively little gain, and as I said, for something that is know to be banned for next year I don't think any teams will implement it.
As for Ferrari, I remember hearing that they were unhappy with they figures from the wind tunnel in mid-late January, so much so they were preparing a b-spec car to fix it. It was supposedly due to the new Ferrari running a higher rake like the Red-Bull but not able to properly seal the floor. Binoto and all the Ferrari team do seem more subdued, although they did say that they didn't want to get carried away with themselves like last year, but I do think they have issues with the car that, as they found it early, they can get on top of.
It's not ideal, meanwhile Mercedes have put in lots of laps, they are showing technical inventiveness in multiple areas, steering/rear suspension/one other, they are fastest and reasonably reliable. The Ferrari looks like last years car, yes it's a bit tighter in a few areas but the concept is the same, the nose looks wide compared to a lot of other cars although we still haven't seen what they have come Australia, because at the moment they will have Mercedes, RedBull, Racing Copy and maybe McLaren in front of them on pace.
