MARTA did an infill station feasibility for Pershing Point (at Peachtree St & West Peachtree St NE), but MARTA costed the project out at almost $300 million. Dewberry Capital went back and revised its plans to come up with a lower cost solution, but MARTA never bit.
http://www.bizjournals.com/atlanta/s...19/story7.html The station was intended to serve the "Uptown" offices that were too far of a walk from Arts Center Station.
Armour was a infill concept that CFPT came up with a few years ago that was intended to provide a multimodal nexus for MARTA rail, commuter rail and intercity rail.
http://www.cfpt.org/pages/armour
Because the Pershing Point location won't really work for a multimodal station, I'd recommend that you use Armour.
For the pink line, is that supposed be the Peachtree Streetcar? If so, it shouldn't connect to Lindbergh, it should start from the south at Lakewood/Ft. MacPherson Station, run by Buckhead Station and end near/or at Brookhaven Station.
For the yellow line since LRT has been studied on I-75, it has always ended at Arts Center. For some reason Concept3 has a route to Arts Center as well as a route to downtown. Not sure what to tell you there...