Sorry but this isn’t a practical solution.
1) second hand converted civil airliners are not an economical nor safe option
2) the 737 is TOTALLY inadequate for the AWACS (INDIA) as a platform. It doesn’t have the power generation capabilities and very well may not have the performance figures to support the full 360* sensor. There’s a reason why only flat arrays are used on the 737 and the large 360* dishes are fitted on larger wide bodies like the 707.
Most of these reasons apply to the tanker role too, just compare the MTOW figures for the two jets, the A330 MRTT is just on another planet. The 737 could almost fit inside the fan of the 777 widebody. The entire point of a tanker is having substantial excess capacity, I don’t see the 737 as a credible option for this role and again there’s a reason why NO ONE has ever ordered it for that role and the standard is widebody aircraft.
Are you saying Wedgetail does not provide 360 degree coverage? Because that is incorrect.
The MESA multirole electronically scanned array radar being supplied by Northrop provides 360 degree coverage and a range of more than 200nm. Unlike Erickson made 2 flat panel radar of Erieye, (or Indian made AEW&C) MESA uses 3 panel arrangement achieving full coverage.
What power supply are you talking about? Did you just make it up? Because engine power/weight ratio is the key to providing necessary electrical power and power to weight ratio of A330-200 military version at 0.52 is less than that ratio for 737 Wedgetail at 0.53. In aviation that is a significant difference. Wedgetail has more than adequate power for all its electronics and cooling needs. In fact, P-8 A/I need more electrical power than Wedgetail!
MRTT or AEW&C? You seem to be confused between these two. A330 might be a completely advisable choice for MRTT but for AEW&C, its large size and excess weight are liabilities.
On average, 737-700ER based Wedgetail burns 2450kg fuel per hour. A330-200 based platforms burn 5600kg/hr. This is very expensive way to monitor your airspace without any additional benefit!
In the past, the electrical and radar systems were large but with new technology, miniature radars provide more power at lower size and electric needs. (Just look at the difference between Phalcon system supplied to Chile versus new G550 based AEW&C of Israel. New one is much smaller and yet has performs better.)
The small platforms are the future for next generation surveillance/ SIGNIT/ C3 missions.
Also, larger A330 is easier to pick up on enemy radar at longer ranges. With developing ultra long range AAM threats, it is not advisable to use important asset on bigger platforms.
Hope this helps
