Distance by Sea (In Kms.)
Between Port Blair & Chennai 1190
Between Port Blair & Calcutta 1255
Between Port Blair & Vishakapatnam 1200
Distance by Air Kms.
Between Calcutta & Port Blair 1303
Between Chennai & Port Blair 1330
Sonce the round trip is less than 3000 km from the above mentioned places in South and East India, MKI's and other medium air crafts can easily reach Andaman and Nicobar islands from air bases in Chennai or Vishakapatnam or Kolkata. IN has a huge Navy Airbase near Chennai in the place called Arakonam named INS Rajali where Tupolev Tu-142MK-E Aircraft are based. And, IAF has air base in Car Nicobar islands. Air force can maintain a sustained bombardment on Chinese forces and supply lines on any (hypothetical) misadventure by China to take over A&N islands. Looking at the geography, India can target and destroy the supply lines from Burma and at the same bombard any Chinese forces that has managed to land in the A&N islands.
The distance between Great Nicobar island and Andaman is about 500 kms. Adding that to the distances you have already mentioned (1200 + 500) means that MKIs with ~3000 km ferry range, cannot reach Great Nicobar from the mainland AND do much good. Maybe with air launched Brahmos or Nirbhay they can do some strikes.
If PLAN gets a beachhead in Great Nicobar, I am not sure the tri-services would like to keep the MKI like advance jets in the Car Nicobar air-base, since it is too close to the PLAN beach head. Maybe LCAs or Mig 21 Bisons. The airbases near Port Blair might be the only one usable for the MKI.
Also, remember that if the PLAN gets a toehold in the Great Nicobar islands, the first thing they deploy will be SAM and anti-Aircraft batteries to deter IAF or IN air strikes.
The sea supply lines from Burma maybe the weakest link, but even those will be heavily guarded by fighters from the Chinese mainland flying over Burma.
Also, the Chinese have built TWO ports in Burma - Moulmein and Dawei (Tavoy) and they are building a rail link from China to Dawei (links below). Dawei is only 550 miles (~800 kms) from Great Nicobar island and can be used to supply a landing force there. Also, PLAAF fighters based in Dawei can easily reach and provide air cover to supply convoys and air defense to landing parties in the Great Nicobar area.
As for all the claims of "India can bomb the shit out of any PLA misadventure in the Andamans - that is the precise reason of this post - to figure out if it is really true, if IA/ IAF/ IN have the necessary infrastructure and if they are preparing for something like this. Also, I never said anything about Andamans, I doubt the PRC would like to invade that far north. But Great Nicobar is the southern-most island, right in the mouth of the Malacca straits and is 500 kms from Port Blair. It has a minimal garrison, no military air field (a small air field however, which can be modified by a landing force to land military planes).
Also, the nearest air base is in Car Nicobar, which in itself is not well defended. So, before the members blow this thread off, I would again appeal to you to see what PLAN/ PLAAF can do and what India needs to do to counter it.
Also remember, this is set for 2020, when IN and PLAN both will have a couple of aircraft carriers.
Asia Times Online :: War trumps investment in Myanmar
Myanmar, China agree to build rail link to seaport - Yahoo! Finance
As for Burma staying neutral, soon, it is expected that Burma will have a power struggle between two factions of the Burmese Junta. India supporting the wrong side (or NOT at all supporting the winning side) may change the Burmese position. Also, PRC is investing in Burma more and more and taking a stranglehold of Burmese foreign trade and international relations (remember, China ALWAYS supports the Junta, India does it SOMETIMES). So, given a choice between PRC and India, Burma may well decide to side with PRC in the future. In international politics, NOTHING is certain - so stating that "Burma will NEVER go with China" is meaningless.
Next, Bombing Burma indiscriminately if it sides with PRC may or may not be feasible, far less a good idea. At that point, India might be at war in two fronts already (Pakistan in the west and China in the North east). Then there would be PLAN in Great Nicobar. Opening a new front with Burma (through the Jungles in the North East) may not be the best idea. India may punish the Burmese LATER, after the war is over, but not right then. So, assume that the actions in the Bay of Bengal area will be more towards taking back Great Nicobar than in punishing Burma.