We can speculate. Cleverly put postulates. Add some logic also to these.
Can we PROVE ?
OR disprove ?
Let me also make my PRIVATE Postulate ::
There have been some queries ::
1. Why Big temple was unfinished .. (especially the not beyond 81 out of 108 Karnas).
2. Was there any ideological difference between RjC with RRC during his later part of life ?
ABSOLUTELY NONE - to query 2. RRC was godified. Search for Godification of RRC. you will find detailed discussions.
RRC Bronze with his wife Danthisakthividangi were taken on procession along with Sundara + Paravai, Sambandar, Appar Trio in front of Thevaradevar with two Ekkalams (long air-musical instrument) one being Rajarajan and other being Sivapathasekaran. RRC was named Periyaperumal and in his 4th year RjC put a vibbodhimadal infront of it... meaning he was godified.
The Periaperumal concept prevailed as we know from Papanasam temple inscriptions RjC 8th year ..
So reverting to the Unfinished works - my gut feeling is :: Panchavanmadevi w/o RRC gifted Thangaiazhagar to the Big temple ...
Big Temple is conceived to be of Akasalingam (ref Archieves again).
With Thalicheripendir etc., etc. it is supposed to be the abode of Cosmic Dancer..
Big Temple is Dakshina Meru.... Another Kailsam on the Southern Part of Chola empire...
For the " Kailsam concept " in southern part - Rajasimha Pallavan - was the First to concieve such concept in Kanchi ... Rajasimhan is considered ROLE MODEL of RRC for this.. His another Role-Model should have been Parantaka I..
RRC added more ingradients of MERU into his Temple... and thus made it REAL "SOUTHERN KAILASAM "...
If Panchavanmadevi (@ Thillaiyazhagiar) promoted the idea of 108 Karanam (and if SHE HERSELF - like Shanthaladevi w/o Vishuvardhan of Hoysala at Belur / Halabedu) posed for various Karanas - after her demise - more appropriately after RRC's demise - the said Karanas could have become incomplete... and no one else - including RjC himself - would ever try to complete it..
With godification of RRC - we can surmise that RjC did not want to excel the levels set by his father-cum-Guru RRC.
He also moved on to GKC .. Created another Brahadeswara .. less grandeur .. less taller..
BUT RjC was not so intensely religous as RRC (rather he could not afford to be either) with his wider contact across the globe ..
Add Social dimension also ...
Like Veeranarayana another LAKE ?
WHY NOT ? then how will it differ from Parantakas ?
POUR GANGES WATER !! MAKE IT " REAL " SIVAGANGA !!
Why another Brahadeswara at GKC with grandeur ?
WHY NOT A SIVAGANGA WITH GANGES WATER ?
like Baheeradharan brought Ganges from the Heavens - Rajendra I also brought GANGES from the NORTH !!
And pick VICTORIES too on the way!!
Call it J-A-L-A-S-T-H-A-M-B-A-M !!
VICTOR PILLAR OF GANGES WATER !!
Want to see MERU in South - go to the Big temple by RRC.
Want to have holy dip in Ganges - go to Chozha Gangam by RjC !