IF this rule were actually true......
(1) Yes I;d take it, if only for a free Lance shot at a vehicle in combat. It'd certainly make me happier when I think about the number of times my Archon has been tied up in combat with a Dreadnought for turn after turn.....
(2) No, I don't think the extreme cost would be worth it for the upgrade PLUS Blast Pistol.
(3) No. I don't think using the pistol would make up for anything, and on any assault units the assault abilities are better than the pistols anyway.
My overall thoughts are that I'm against the idea. I think I prefer pistol rules to stay as they are.
If something of this nature were forced in, I'd rather replace the extra attack for charging and make it act as a counter-Overwatch as it were. You declare charge, opponent overwatchs, then your pistols get a similar snap shot in return, then combat happens (like a snap-fired Hammer of Wrath).
But replacing the extra attack for CC weapons with firing a pistol, in my opinion, is a really stupid idea.
EDIT: I'd also like to briefly say that a LOT of the rules I've heard about being from 7thn edition so far sound REALLY stupid, and are frankly too far if this is supposed to be a "minor" update. I've heard about this pistols things, a possible change to a percentage based force building thing, a complete change to combat resolution and consolidations, all of which sounds to me too major for a rules set everyone so far agrees will just be a 6.5 rather than a 7th.