So, as an additional question, IF they chose to remain apart from the Federation, but joined the Star League, how would something like THAT change the future?
I...don't know.
The Hindu Collective is an unprecedented situation for the Star League because it's so...tiny. And that raises lots and lots of questions.
I mean, the Houses pretty much received equal voices in the High Council, other than the first-amongst-equals Hegemony. They were pretty much the same size, too, other than the smallish Hegemony, which made up for it's physical inadequacies with a powerful military, more powerful economy, and big, fast cars. So, the "one House, one vote" system worked.
Then there were the Periphery nations, which joined with a boot on their neck. If they ever got votes in the Star League as something other than "wards of the state," I don't think it's well attested. So, those potential examples of small states having a say in the Star League...aren't examples that can be used to judge the Collective.
So. Cameron's putting together the Star League in the 2550s-2570s. The Houses are convinced one by one and hear that the Hindu Collective is on board...how do they react to the idea of 17 planets having a voice equal to their hundreds of worlds? Do they care? Does the Star League coin a US- or Terran Alliance-like "Great Compromise" that gives voting wait based on planets/population/wealth?
Thinking about this...I find the former unlikely. The House Lords won't like the precedent of little states matching their say on the High Council. What happens if some other little state joins, like a Periphery nation colonized during the course of the Star League? At the time of the Star League Accords' signing, it wasn't clear what the Periphery states would do - join, sit-out, get conquered? Those are four more relatively small/weak nations that would have an inordinate voice under "one nation, one vote."
The alternative - some form of proportional representation, be it a US-like bicameral "Star League Congress" or a unicameral "High Council" with weighted votes - so radically changes the Star League that it makes any further prognostications difficult. The dynamics and scheming of the Houses will be changed by the new rules.
The conquered Periphery nations may find themselves with some de jure representation on the Council, albeit weak because they're, well, small (and, if it matters, poor). But how do the Periphery states react in the long run to that? An excuse to rant against the League and try to throw spanners in the works? Do they simply get pissed because the huge weight of House votes tramples them as the Inner Sphere exploits the Periphery? Or do the Periphery states gradually become "part of the system" in the Star League and get over the whole "brutal conquest thing"?
There are a lot of plausible outcomes and no precedence to really go one direction or another. Feel free to pick amongst them.