I have seen a few people suggest this on other forums and I have thought of this as well.

The ultralisk is a great unit except for its inability to get into melee range with zerglins and roaches (I know they are a ranged unit, but it is an exceedingly short range) running around.

To fix this, the Ultralisk should be given the ability to walk over units, much like the Colossus.

Another idea, would be allowing the ultralisk to act as a shield for zerg units under it making them unable to be targeted.

I would just like to see some Ultralisk viability and right now it doesn't feel like they are getting much love.

We're aware of the situation of the Ultralisks.
We're going to work on them in order to make them more useful in the next patches.