Akash is not a tactical ABM for christ sake! It is as you correctly pointed out, India's first attempt at making a medium ranged SAM,and it shouldn't surprise that they tried to copy a proven design(or atleast parts of it)-SA6.
The guidance and control and control radar is entirely Indian dIndianigned right from DMPS(dual mode ferrite phase shifters) to TWT.
One of the requirements of ABM radar system is very high pulse repetition frequency- something that our rajendra lacks.Not to mention the fact that it's range is severely limited to just 100kms(after all it was designed more than 25 years back!). More recently designed Indian AESA radars have a range of 400kms against a 2m^2 RCS.
Lastly I'd like to point out that no country shares their painstaking research with any other country. For instance Russia never helped india overcome various types of Combustion instabilities that we were facing in the development of CE-12(India's first attempt at designing a cryogenic engine,circa 1987-gas generator cycle).
Umpteen number of problems crop up when one get down to design a system or even tinker it especially when that phenomenon is less known.[/QUOTE