The belly button really represents scar tissue that extends from the skin to the muscle wall fascia, and as such there are no vital structures. It is possible to perform tummy tuck without replacing the belly button, but this will impact the appearance of the tummy. In some instances the belly button has become so stretched and elongated that it is virtually necessary to remove it, but this is the exception rather than the rule. In most cases people are concerned that the belly button won't appear normal as this is normally an important aesthetic landmark on the abdomen. However, if you are committed to doing without yours, and you are fully informed of the implications, then I think it can be done. Just remember it is much easier to remove a perfectly good belly button than it is to reconstruct one down the line if you ever change your mind.