I would not skip the hydrotest. I am not entirely certain (would have to dig out the code), but I believe ASME VIII requires a retest after any modifications. If this is the case, any legal vessel with a current Stamp that needs a modifications would be fraudulent if it were to not be retested.
The amount of liability there is not worth any price tag. Even if something were not to happen, I think the ability to sleep at night is worth the hassle. Hydrotesting is not a "you should do it so it looks good" or a "you should do it so the equipment can function" requirement, its a "you should do it to preserve human life" requirement.
Even if it was legally acceptable, ethically I think that would be very wrong. You wear a ring to remind you not to cut ethical corners, don't cut this one.