I agree with you in principle, but I can think of 2 reasons to crossbreed:What all are your reasons for crossing beautiful Wellies with other breeds? For fun? For genetic hardiness? For certain egg color? The offspring of cross-breeds won't breed true so -- not judging -- just wondering. Something to consider is hatchling mutts will be hard to re-home should an emergency occur where they might need to be placed - unless there are plans to raise the mixed offspring for meat? For myself I've kept my breeds true and relieved I did because I had to re-home several bully hens that turned out easier to re-home because they were not mixed breeds. In the city it is more of a challenge for us when it comes to finding homes for unwanted purebred cockerels let alone mixed breed males. I had to travel several counties away to find a rescue home for unwanted cockerels/roos to place a rare cockerel that was shipped to us by mistake and it would've been a tragedy to eat him! In our local feed store the back room is filled with cages from owners of beautiful purebred roos that can't find homes because of roo zoning restrictions. The mixed breed males don't have a chance in Hades of even finding a free home unless it's for someone's dinner table! We've made our flock into such personable pets that we can't eat them -- DH will do his best to find even the mean ones a home rather than see them go to a dinner table LOL!
1) for fun, to see what you get. No harm if you have a plan for the progeny. Our very best layers are the "so called" barnyard mixes. Some are such pretty birds I wish I could get them true breeding.
2) breeding project to get new colors. I created a Crele Welsummer, more commonly called a Welbar. They are definitely larger and stronger than the purebred Welsummers (I believe my Welsummers suffer from inbreeding depression, so I am not breeding them anymore). But the best part is that Welbars are 100% autosexing, no more roosters coming back from customers because I sexed them incorrectly. I also think it would be fantastic to make an Isabelle Welsummer (add the lavender or self-blue gene). Any of these breeding projects start with crosses to other breeds. Since it is planned (often out to several generations), this is obviously not the same as the random crosses you object to, but the intervening "cull" are really just barnyard mixes. I put them into out laying flock and they do quite well for themselves and us.