Interesting points of view re liability for those undertaking conversions or changes to the original structure of firearms.

The bolt action equivalent, apart from say rechambering or rebarreling, would have to be opening an action up for a longer cartridge, a relatively common practice since the earlier 1900's undertaken by some of the most known, trusted and skilled firearms makers both in England and the USA.

Many standard 98 Mausers were opened up for the 89.7mm long 404 cartridge, the 91.5mm long 375 H&H cartridge and the greatest of all would have been the 95.3mm long 416 Rigby cartridge.
The most famous of the latter being Harry Selby's Rigby 416, at least a couple of times returned to Rigby in England to be rebarrelled.
While the gunmakers and smiths removed as much from the rear of the action as they could, all of them required some considerable work on the feed ramp from the magazine which of course serves as the lock up for the lower bolt lug.

I was always a little surprised/concerned to see the amount of work made on the feed ramp/lower lug recess on my own Type A Oberndorf Mauser when I became aware of 'concerns' expressed on forums several decades after having owned my Mauser, but my fears were well and truly allayed when I saw photos of the work undertaken by Winchester on their pre'64 M70s for the 375 H&H cartridge. Winchester did not make pre'64 actions in 'magnum' lengths, only standard, and opened them up with work to the rear and front of the magazine well and feed ramp. Photos of my Mauser and a M70 in 375 H&H show identical modification to the feed ramps on both actions.

To my knowledge nobody has ever had an opened up Mauser or M70 fail. All of this may only show the great inherent strength of bolt actions or the great weakness of double rifles, or it is all just a big puff of wind.