Don't judge all P14/1917 actions by one example. I agree, the cock on closing in military configuration does not work for me, however I have 1917s that are extremely slick operating, better than my Mausers. I have fourteen P14/1917/Rem 30 actions here between project rifles, bare actions, complete actions, and finished rifles. Some do work rather roughly due to cock on close, age, corrosion, gummed up lubrication, etc. However the ones that are complete rifles and currently in use are extremely slick. These actions have much less bolt wobble than Mausers, and are very slick operating. I like Mausers too, don't get me wrong, but the Enfields are slicker when set up as cock on open. I have Mauser 98s in 7x57, 30-06, .375 H&H, 458 WM, and I prefer the Enfield style actions.
Aftermarket parts are indeed harder to find and/or non existent as compared to Mausers, valid concern. However a competent builder can make a first class DG rifle from these actions. Not all of them have the "duck pond" on rear receiver ring, Remingtons and some Eddystones do not. Winchesters and some Eddystones do have the "duck pond." A big plus to using these actions for builds is the bolt handle and safety are good to go for low scope mounting, unlike the military Mausers. The dog leg bolt handle is a cosmetic issue some do not like, not a functional one, and can be changed easily. The Enfield actions are definitely better suited for magnum length cartridges with less "shoehorning" required than the M98. As far as the receiver ears, I would not cut ears off a non-modified receiver. There is a glut of these actions that were already modified in the 30s, 40s, and 50s during the heyday of the sporterization era that I would not consider cutting an unmodified receiver. There are so many that are already cut that this is a non-factor in my opinion. I just counted 44 1917s currently listed on Gunbroker that already have the receiver ears cut off in sporterized condition. A non-factor, cut receivers are more than plentiful.
One other important point when building a DG rifle with these, use a coil spring ejector ! The weak point of these actions is the leaf style ejector spring that are prone to breakage. Remington changed these to a coil spring setup in their Model 30, and it is easy and inexpensive to change to a coil spring ejector on the military actions.