OT
Deceleration based pressurization can't push water uphill/ against deceleration (unless you have a piston denser than water). Having the water tank in the nose could cause self pressurization due to reentry heat.
Shuttle deceleration was under 2 G due to long time spent in thinner upper atmosphere (benefit of lifting body.
Could also have smaller than insect size holes or keep air flowing out of them when outside. Need to deal with being on Mars (dust wise).
Agree on failsafe.
If that backup works, what is the advantage of the primary steam system?
I wonder if it would be similar to the Saturn V engines which used the turbo pump exhaust as a thermal barrier in the nozzle. Feeding water at the leading edge would cause a steam barrier of rapidly expanding volume that keeps the reentry plasma away from the skin. Wouldn't need holes along the entire surface. Sort of like the water drop on a hot skillet trick, water skates around on a steam barrier instead of just boiling off.