Twin ET-derived heavy lift vehicule?

Hi,

Crazy idea of me (again):

ET/Shuttle derived heavy launcher have developpement costs associated
with the modification of the external tank structure to accomodate
different structural loads associated with a different configuration.

If you were to design a vehicule that would be attached between two
external tanks, both equiped with the two appropriate solid boosters,
and used disposable engines capable of delivering the equivalent of
thrust and performance of 5 SSMEs, wouldn't it be possible to deliver
nearly 150 tons to LEO, in a single shot?

Since a fully fuelled ET with two SRBs and 3 SSMEs can get 80 tons to
orbit, it seems reasonable that 2 fully fueled ET with 4 SRBs and 5-6
SSMEs can get 160 tons to orbit, no?

Beside ground handling problems, what other technical problems could
prevent such a scheme, from a technical point of view?

From an operational standpoint, would it be preferable to drain both
tanks at the same time, maintaining a CG within the center vehicule,
or drain a tank almost completely, reduce thrust to minimum or
shutdown the engines, seperate, and then resume on the fuller tank?