I actually think that B1 is too low of a bar for attaining citizenship. You still can't participate in Estonian society on anything other than a superficial level as noted above, so I'm not sure how you can constitute a "citizen" on that basis. Naturally there has to be a high degree of arbitrariness, and that's precisely the point — whilst B1 level might be sufficient in German or French (I understand that it is the benchmark level when applying for citizenship by naturalisation of those countries too), Estonian is, well, much harder than those two languages and, far from making B1 the greater "achievement," in fact means that a B1er is still going to flounder in everyday situations much of the time. And that's even before we get on to people who just take the test simply to scrape through.
B1 Estonian exam, Part 3: Certificate and conclusion
An alternative might be to judge cases on their individual merit, which is always a nice thing to suggest but likely to be found wanting in terms of resources.
If and when I should get to B2 in Estonian, I'll revisit the topic and see if my own citizenship level demand hasn't pushed the bar even higher, to C1. Hopefully not!*
The first and second parts of this story arc, including pointers on how to take any of the level exams, from A1 to C1, can be found here and here.