Commons and JPS will most likely be suspended from trading when recap/release is announced. Therefore, there will not be this "boom to the moon" - allowing trapped commons to sell to "greater fools".
But also, as a plus, no common holder would see the devastating crash resulting from heavy dilution due to SPS-to-common conversion. I guess it would be - in theory - a crash from 50 to 0.25 cents (or lower). When the reverse split and the capital raise are completed, holders of commons will most likely find new shares (ticker: probably FNM) in their securities accounts.
But it won't be a great "deal". Someone who now holds 10,000 FNMA at 50 cents (value $5,000), should afterwards hold e.g. 50 FNM shares at $50 (value $2,500). In effect, It's like FNMA falling from 50 to 25 cents now.