I can fit a 29x2 tire in my fork, but that's of no use when there's a limit of 35 in the rear. you could say "the front end writes checks that the back end can't cash" when you do that. personal experience with unrepairable tires in the trash can from slashes and severe pinches, always the rear, back this up. a skinny tire up front is actually preferable if I had to choose one or the other, because most of your weight is on the rear wheel and it's much easier to loft the front tire over and steer around tire-killing obstacles. the challenge is part of the fun but it stops being fun when you slice a tire wide open and have to walk 15 miles home—been there, done that. I tried modifying my frame and tried a 650b rear wheel with no luck. I am about to get a new frameset just for this reason. I enjoy riding a rigid, drop-bar bike on trails enough that it's well worth the cost at this point.
Sounds like it wouldn't work for you, as you are probably getting those tires sliced up on the rocks around Austin.
But, it is my preferred way to ride. Did a practice race yesterday set up like that (50mm front, 38mm rear). Works great, as I can go low pressure in the front, and get all the flotation and bite and cush I need, while the low rolling resistance on the rear is giving me the lightness and speed I crave where it counts.
You are correct that there may be 50% more weight on the rear tire, so plan accordingly. That means that most of the rolling resistance is coming from the rear (especially on 1000+ watt accelerations). Personally, I have seat post & frame that are compliant enough where it does me no good to have a larger tire in the rear. Don't need it, wouldn't want it. Of course, if I hit something hard that is bigger than 40mm in size, I'm risking a pinch flat. I'd never ride a fatter tire on there rear on gravel. (although on a road bike with tires below 29mm I sometimes do for the reasons you mentioned)
Another way to look at it, is that no MTB is rigid front & sprung rear. A fat and low pressure front tire is somewhat akin to a front shock (with short travel, lol).
I'm kinda thinkin that if you are getting slashed tires, its not the size of the tire that is at fault - you need a beefier build. But if you are getting pinch flats - yeah, you need more.
Anyway, I'm just throwing an option out for people who don't feel the need to put mountain bike sized tires on front and rear.
Rear tires get the damage partially because the front throws up debris at them at awkward angles and partially because it carries more weight.