Israel ought not commit to an immediate ground offensive. It will cost them significant casualties among their ground forces. Rather, they should use their superior air force, tell the people that live in Gaza that they have 24 hours to move out of an area, then obliterate as many buildings in the area as possible using large caliber bombs and cruise missiles. Only then should they move in with ground troops for mop up duty. When they've achieved total control of that sector, they can then repeat the process. Issue a 24 hour notice for all civilians to leave a sector, then turn every building in the sector into rubble using air strikes and artillery. If people don't leave, they will be buried in the buildings as they are destroyed.
Rinse and repeat until you've pinned the populous into an uncomfortably small area, forcing fellow Arab states to take them as refugees. Those who refuse to surrender can be treated as allies of Hamas and killed without question.
A clean, highly organized, assault on Hamas and the people that happily support them. Strip the emotion out of the scenario and focus on executing the mission at a high level. Clearly, the idea of sending small numbers of special forces into Gaza and trying kill selectively kill Hamas members does not work exceptionally well. Bring up 100,000 reservists. Get your F-15s, F-16s and artillery working over time and just lay waste (from range) to anything that Hamas can hide in, whether it be resential or commercial. It's a relatively small area and Israel has the military capability of steam rolling the area. This is the right time to use that capability.