Theoretically, MTGE can sell $1 bil of agency MBS. At 8.5:1 leverage that would free up $118 mil in equity capital. MTGE can then use the proceeds to buy back 5.9 mil shares (9.9% of oustanding shares) @$20.15.
BV accretion would be 32 cents per share assuming BV is $22.50 at quarter end (thus BV would rise to $22.82). It would be fairly neutral to EPS and the dividend/sh if leverage is kept about the same, would allow MTGE to cherry pick and sell its least desirable assets without incurring EPS or BV dilution, perhaps keep the hedges the same (thus boosting the hedge ratio), and change its portfolio mix to more non-agency to protect itself even more against rising interest rates.
Do they have a buyback in place? If not, then the risk of such a plan is that they have to announce the buyback first. That will likely drive up the share price decreasing or removing the benefits you mention. Also, such a plan cannot be executed quickly at all. Given volume restrictions on buybacks it likely would take at least a calendar month. A lot can change in a month these days.
$50 mil buyback announced back in October 31. They used a little of it to buy back 300K shares at $22.76 in 4Q. So $43 mil remains on the authorization. The buyback was 2 cents accretive to BV at the time. They could easily complete this buyback and authorize another.