My only concern with a variable level park like that, is that unless it's well designed, it could result in asking people with mobility challenges to use multiple elevators just to go across the park from East to West. Which is less than ideal. Parks should focus on being accessible to all, before we get into what is more conceptually exciting. At the very least, the park needs to meet the street at the same level. If the park requires stairs/elevator to access in the first place, it's doubtful it would be a particularly successful park. We need something people can casually walk into, regardless of their level of mobility.
I agree about the park being linear along the south edge (or north edge, either works tbh) is a good idea, but they need to ditch the idea of a parking structure below it that they had in the original design. The park should be at street level. Otherwise it will likely be only used by condo residents, which is a total waste. Hopefully the end of parking minimums makes that possible.
Also totally agree on doing a more westward rail deck park. I'd always hoped that would end up being a future phase of the city's plan after this section was developed, and since this is now out of the city's hands, might as well focus somewhere else.