When you say "magazine rifles shot cross-handed helps a ton for alot of situations...", are you saying to shoot right handed (right hand is trigger hand) with a magazine rifle, even if you are left-eye dominant? How would you line up the sights? Do you hold it with the stock against your left shoulder, but use your right hand as the trigger hand? I've never tried it that way. Seems like it would be a little awkward. I just switch to left-handed for rifle / shotgun, but stick with right-handed for pistol.
No, not sure how that would work out - I just meant being versatile in the left eye /left hand on trigger or right eye / right hand on trigger, whichever isn't your "go to" side.
The simple way like you were initially thinking - being able to go totally to the non-dominant side & shoot with some level of accuracy is an asset - esp like in hooch-style duck blinds (dirt coffins don't matter) -or even as simple as teaching someone new to firearms that you take to a traditional range - if you normally shoot left (like me) but can go right (really helps whoever you're teaching so they only have to "copy" you), that is like the picture being worth a 1000 words - that way they aren't translating while learning.
Then there's always the argument for it in relation to 3 gun type match/contests - we do a super informal version among friends & my "go to" being left helps a ton in the AR- part shooting from behind a barricade/cover where the righties have to stop & think where I just flop the rifle to the natural shoulder & sight down my L eye & the occasional spot they rig a "right hand only" blind (or ergonomically a contortion to insist on shooting left), having practiced shooting R gives me a 40/60 of hitting the mark.
As a kid I was a pure leftie, but I got Lasik in my R eye 4-5 yrs back & that's opened a ton of situations - I still can't shoot a RH bow worth a dang, but prior to Lasik I couldn't hit a duck shooting rightie ever. And being able to shoulder up to either side means I'm not always automatically kicked to the far left slot in the hooch-duck blind- but part of that one working out so well %-age wise was because I added a cheap holograph/red dot to my shotgun too (I recommend - money well spent.

There just happens to be a pawn shop on my way home from work!