dave, doesn't surprise me something is being built there now.
Just wanted to bring this thread back to life temporarily with some more drawings.
An overpass for Nantucket Dr at this point in time is a waste imho. Reasons being no development on the other side of the freeway, and the close vicinity of a creek and the speedway, I'd doubt anything being built there, specifically residential development.
This layout just shows a new stretch of road from the frontage rd to Old Arrington Rd, which could convert the existing stretch of the Frontage rd from Old Arrington to the Speedway exit into a two way traffic road like it was before. Except with this layout, NB traffic would join old Arrington and end at Grand Prairie Rd. Much cheaper option than going with constructing a new overpass.
Now heres where the money saved could be spent, a new interchange for Hwy 6/ Texas Ave.
This layout is similar to the one I posted earlier, except in this one Sebesta Rd is extended to Deacon Dr.
With the ability to use Deacon Dr/Sebesta Rd to get to Hwy 6 NB, this configuration could alleviate traffic from the RP interchange, that being if people take Welsh to Deacon, Rio Grande to Deacon, Longmire to Deacon, etc.