I'd add a few more points. A naval base needs some hinterland to supply it. Otherwise, all supplies need to be carted in from home and stocked up. It's all fine and dandy to say that China can do all that in an Maldivian island, but those supplies will be the first target in the event of hostilities. Secondly, storage for these supplies: even if China manages to strengthen some logistical supply chain, their storage cannot be easily defended, as most, if not all Maldivian islands lack natural cover, mountains, etc. into which they could build underground facilities. The entire country has an average elevation of about 4 feet above MSL. There is also the minor issue of corrosive tropical air - they'll need to protect their storage. Same goes for placement of air defence units around these facilities - do they have good locations for such units? I'd urge folks to look at what the great khan was able to build in the best location in the area - Diego Garcia, and compare that with what the Chinese could do in not so great locations. Also keep in mind that the IOR is not hostile waters for the US.
I am not saying the above in terms of a fait accompli that the Chinese have a toehold in the IOR (however nebulous it may be). Instead I am saying that these considerations will go into Chinese calculations on whether to build up some facilities. Given a choice, they'd take Hambantota** for those reasons without a second thought. But Hambantota is not really working out, given the SL govt's clear stand on not allowing mil facilities in the port, and handing over the nearby airport to us (it's hardly 15 km away as the crow flies). I am sure a Sukhoi can cover the distance much faster
. So the Chinese are really left with Gwadar and maybe Sittwe, though Myanmar will not roll over as easily as the bakis.
Gwadar is a concern, and perhaps our only concern. That's where Chahbahar and Duqm come into play. The latter is openly for our military usage. Djibouti is too far to cause us any damage, and we seem to be up to something there anyway.
So given the above, what are China's options? They don't have a good staging area in the IOR, so they have to deploy from home ports only. What will they do then? Send a nuke sub to harass our shipping? Sure, they can try that. I am sure despite our watching the ingress points, they could slip in once or twice without us knowing - after all, it is not easy to be in a watchful state forever and the IOR is not a lake. But note that I said nuke sub, not diesel (the distance is just too much for diesels to operate without replenishing supplies). But sending a nuke sub to harass shipping is a serious escalation - will they want to risk that? We could do the same, and with friendlier ports for our replenishment near their home waters. And unlike us, their shipping lines are easier to reach from our mainland, let alone locations in Lakshadweep, A&N, Duqm, etc.
My reading is that China will do everything it can to try to advance inch by inch without actually pushing us beyond our redlines*. That's nothing new - that's what they do in the mountains. In the naval arena, that means sending ships on token anti-piracy patrols with 3-4 ships, and leak the news to our media, which immediately like BRF (of late) will do rona-dhona, completing the job for them. We will all live in a state as though Chinese ships are permanently anchored off Marina beach. But beyond that, they won't really try anything, as their logistical chains are simply too long and unsustainable.
Eventually, things will settle at an equilibrium: they'll keep ICS under their thumb and ensure they have safe waters for their nuke boats (East China sea is not that safe given Japanese and Unkil presence right off their coast in the first island chain). Or they could hang out in the Yellow sea, which is even worse, given SoKo and again Unkil. Similarly, the IOR will be under our watch, specifically the ingress and egress routes. There will be the occasional pin-prick by both sides, but that's pretty much it. These games on some atolls here and there are sideshows.
* We have a responsibility to not get accustomed to moving our redlines as the Chinese push them. So if the current noise is too much, we should overtly signal some action: exercises in the ICS with Vietnam would be a nice start, accompanied by massive publicity. We should simply prevent them from pushing our redlines, that's all. No need to send troops to Maldives - it's not worth it.
** For a long time, there was so much hand-wringing about China in Hambantota - how has that worked out for them so far and why? Something to ponder about.