The happy medium here would be what they're doing in AA this year. Shifts are still allowed, but all four infielders must have their feet on the dirt. This bans the 2B from acting as a fourth outfielder but still preserves the strategic intent.
I've seen ~10 games using this rule and to my eye it looks "right." Hard-hit balls tend to go through and the extra fielder tends to scoop up the seeing-eye type hits, and those still come at the penalty of more balls going through to the opposite side.
This makes some sense. The one hopper that's smashed but picked up by the rover / deep infielder I think is the most frustrating play. Otherwise, I'm OK with shifting. I think it is too fine line drawing to say you can play the SS up the middle and the 3rd baseman over towards the SS normal position. When can the SS move to the 1B side? After the ball leaves the pitcher's hand? On contact? Rules on positioning are a bit like the old NBA rule against the zone. The zone wasn't the problem, the shooting was and the failure to spread the floor.
