^I like the thinking but what I hope happens is that eventually all the buildings (except the Carnegie Library) between the Capitol building and 7th Ave between Washington and Jefferson are demolished or moved. The warehouses on the Eastern edge of that stretch would hopefully be moved into the warehouse district South of Downtown to help fill it out. The other government buildings (Court of Appeals, AGs office) are heinous and anti pedestrian and likely will eventually need to be replaced and obviously theres numerous places they could go.
Id like something along the lines of this plan from the late 60s:
Now obviously the mall it shows there couldn't exist today because of the awful O'Connor court building and such, but Id like to see it happen from 7th Ave to the Capitol. On the block bounded by 7th, 8th, Washington & Jefferson Id like to see a 100 meter/yard copper clad obelisk commemorating Arizona's centennial.
8th and 9th Avenues (and possibly 10th as well) between Washington & Jefferson would be eliminated to allow for a contiguous park space. Bellow ground would be an expanded Capitol Museum with exhibits on the 5 C's and all the Arizona State symbols, including aquariums/enclosures for Apache Trout and Arizona Ridenose Rattlesnakes, ringtail cats, cactus wrens, Arizona tree frogs, etc. The Jefferson Westward Expansion memorial in St Louis is set up in a similar way, below ground, beneath the Arch and thats how you access the elevators to the top of the arch. The Copper Centennial Obelisk could have an elevator/stairs as well up to a viewing platform.
I'm also not sure zoning for a new tallest is appropriate or even desirable in the Capitol Mall area. Central Phoenix is already vastly over zoned for high rises, we can't fill our current high rise zoned lots, no need to create more. I'd hope the Capitol Mall could keep its current midrise profile, but with a lot more variety of midrises that include retail, non governmental office, and of course residential. I really like your idea for a neighborhood shopping street along Adams.
To make up for the huge lack of places to get food in the Capitol Mall area (all workers must either pack lunches or drive out of the area)
Food Carts like are so prevalent in Portland should be encouraged. They could park along the expanded Capitol Mall park on Jefferson and Washington which would lead to an activated park where people would eat and it would serve area workers as well as tourists to the Centennial memorial.
Finally, if memory serves the idea for the placement of the new House and Senate buildings was to be the lot bounded by 19th, 18th, Washington and Jefferson. I believe they need quite a good deal of space for their expected future needs. And heck, while we're dreamin', lets knock that heinous Executive Tower down and incorporate its office needs into the new House & Senate buildings on the aforementioned lot.