Using COJ's GIS system, it appears that there is 70' of ROW on both Monroe and Duval. The length of both blocks is about 315'. Closing off each street and expanding the park's boundaries to the adjacent buildings adds approximately 22,050 square feet. Add those two up and you get 44,100 square feet, or just over an acre. Incorporating both those blocks increases the park space from 1.54 acres to 2.55 acres.
If you close off Laura, you add an approximately 14,400 square feet (60' by 240') or . 33 acres. With that addition, you nearly double the park's size from 1.54 acres to 2.88 acres. If you further the road closing on Laura between Adams and Monroe (the holy grail of road closings), that number jumps to 3.27 acres. Closing Laura between Adams and Monroe opens up fantastic outdoor dining and block party possibilities, and would also serve as a great entryway into the park.
Now of course some of that park space "added" is already a functional part of the park, and some of it would have to remain bike/ped space, but it still would open up significantly more design options IF there is going to be a major overhaul of the park's design. Not to mention, it would make the park and surrounding uses significantly more pedestrian/park user friendly.
I'm going to pick the brain of an engineer and see what possible impacts there are for closing all those roads.