Actually, the underground stretch from Warisan Merdeka to KLCC really has good potential to be developed into an underground haven for the following reasons:
1) It will be linking the 2 tallest buildings in Malaysia.
2) The ongoing MRT project will have a 9.5km underground stretch from KL Sentral to Maluri passing through Warisan Merdeka & Bukit Bintang.
3) If everything goes according to plan, the underground stretch can link all major shopping malls & land marks in Golden Triangle. Warisan Merdeka - Plaza Rakyat - Pudu Jail Redevelopment - Pavillion - KLCC - TRX
4) If the government have plans to develop Bukit Bintang into a world class shopping district like Orchard Road (Singapore), Ginza (Tokyo) & Fifth Avenue (New York), linking the shopping malls through underground passage makes more sense bcoz:
a) Take advantage of the current underground MRT project.
b) All will be sheltered from the sun & rain.
c) Land above ground is limited & expensive.
d) Ease traffic congestion.
Those who have been to Japan should get what I mean. They have like another city under the city (a bit exaggerated of course) with abundance of f&b outlets, shops & shopping malls underground. It makes walking from 1 place to another pleasurable & faster (no traffic light).
The above are just my personal point of views.
undeground retail or walkway only limited to stations area which may stretch out a lil to reach out to the adjacent buildings. these structure is impossible along the tunnel track