So, unless we can trade House and Allen for a backup wing with the ability to defend and shot from distance consistently (and I have no idea who this player can be; they're very rare), I don't think they're expendable.
Well what if we sign Robert Horry? I know he would play at the Pf and C, but he can definitely hit the outside shot on a consistent basis and he is clutch. We could then use Giddens or Walker(which ever one we don't trade)for strictly playing tough nose defense and don't worry about offense except for cuts to the basket and finishing at the rim(we know walker can do that ).
Walker and Giddens? Walker struggles to guard D-Leaguers, from what I saw, let alone the LeBrons, Hedos, Johnsons, Ginobilis and Kobes of the world. I don't think those guys will play. Horry can't play at the wing, and he looked finished the past two seasons anyway. Scal is better than him, I think.
The approach you expose in that reasoning, it's basically the substitution "by committee" I've heard during the Summer re Posey (Powe would rebound, Tony would defend, House would shoot, etc.), and is quite absurd, I think. I believe it may work in some other American sport I don't know, baseball, football or whatever, so people bring up the concept all the time, but I never understood how could it be applied to basketball. With that logic, you can replace virtually every player, Garnett, Pierce, whoever, by bringing 4 or 5 guys who, among them, can replicate their skill-set. The problem is that you can only play 5 guys at the same time. So, I really don't see a play-off rotation which includes Giddens+Marbury+Horry.