First of all I will like to tell that I am having a hard time deciphering your English.
Examples:
Service and support is quite wanting for these companies in India
I didn't understand what this sentence means.
there's a lot more on hand for the lenses
I thought you meant to say that sensor shift stabilisation will aid more on top of in-lens stabilisation.
Anyway, now to the main part:
Look, I don't want to argue with you, as these type of discussions have a tendency of going out of hand and escalate into flame wars, but do note the following:
Availability of lenses - the sources are normally the same - if not the official outlets, the exclusive importers(customs notified guys) or online. I believe bhphotovideo has an India exclusive site, so it's quite direct and no need for the customs notified guys unless you get a better deal

. Global Easy Buy on ebay is perhaps another.
You are seriously comparing availability of lenses of Canon and Nikon in India with availability of lenses of Pentax et al in India? Go to 100 shops which sell lenses, and see how many lenses they have for Sony, Pentax etc.
You are suggesting alternatives like online buying and importing from abroad? I have nothing to say in this regard. Be happy with your Pentax gear. We are happy with wide availability of lenses for our Canons and Nikons and at the correct price.
For the most of what I have learnt, IS in lens or by sensor vibration is equally effective. Just that they differ in that the one advantage of in-lens IS is that the photographer can view the image shake directly
1. They are not equally effective. In lens stabilisation is more effective, typically to the tune of 4 stops. Sensor shift gives 2 stops.
2. You said just the opposite: With in-lens stabilisation, photographers will not see any shake while taking photos. But with sensor shift stabilisation, the image will jump around when you look into the viewfinder, for long focal lengths.
advantage of in-camera IS is that quite significant sums of money can be saved due to the lack of necessity of IS in-lens
Of course, why would you spend premium on them while you already have IS in-camera!!
1. You yourself gave options of lenses for Pentax etc is GlobalEasyBuy, importing via online purchase etc. So you still think your money is saved?
2. Sigma 70-300 non OS version costs 7.3k and 10.5k. OS version costs 25k. Do you think the price difference is only for the OS?
Tamron 70-300 non VC costs 7.3k. With VC costs 25k. Do you think the price difference is only for the VC?
Nikkor 70-300 non VR costs 6k(?)
With VR costs 25k.
Do you think the price difference is only for the VR?
Then I am afraid you are wrong. The price difference is due to the optics - sharper pictures (hell and heaven difference than the non stabilised versons), less chromatic aberration, less pincushion and barrel distortion. Better AF. Better build quality. Internal focussing motor. Distance scale. Better contrast. Choice of glass elements. The cost is more due to these factors rather to these factors.
Just for your information,
Tamron SP AF 70-300 VC which costs 25k and has got awesome reviews - the price is same for Sony mount as well, but for Nikon and Canon it comes with VC in lens, and for Sony it is without VC. But costs same. So I guess you got the point about image quality and general performance of a lens.
Also, do give me a functional link of B&H Photo India site which is actually of any use.