And human rating is a NASA requirement they won’t have to worry about for a few years.
It would also be interesting to see them do shallower dips into the atmosphere then pull back out and repeat. Like a skipping stone. Lots of expansion contraction, but might work better without tiles.
There's no materials science breakthrough needed -- the shuttle used ceramic tiles successfully its entire service life. What's needed is engineering work, and that's what SpaceX has been doing.
We’ve seen much larger holes than that in previous tests. Some of the control fins burned completely through.
The quarter thing may have been true for the space shuttle, that doesn't make it true in general.
Here is a decent summary.