To date Berkshire's stock repurchases have changed IV/BV very little. Since Berkshire began regular repurchases in August 2018 Berkshire has repurchased 12.0% of its outstanding shares at a weighted average P/B of 1.34. If you include the repurchases in 2011, 2012 and 2014, Berkshire has repurchased 12.8% of its outstanding shares at a weighted average P/B of 1.30. If you estimate IV/BV was 1.50 at the start of regular repurchases, the repurchases have pushed up IV/BV to approximately 1.52. If you estimate IV/BV was 1.60 at the start of regular repurchases, the repurchases have pushed IV/BV up to approximately 1.63. The numbers starting from 2011 are very similar.

I would argue that BV per share remains one of the best metrics for estimating IV, and especially for estimating the percentage change in IV from one point in time to another. Pretty much all valuation methods, including all assumptions within each valuation method, lead to IV/BV estimates of 1.5 to 1.7. This may seem like a large range, but in fact it's quite small, just +/- 6%. No valuation method is accurate to better than about +/- 6%. I probably don't know the value of my own house to better than +/- 6%.