This is stupid, lemme explain why:
1. The beginning: basicly what you described by "you can breed a comp for less that its price on gtl" is how comp trading on gtl works, because people want to make a profit. (also shiny breeding is way more than 20mil if you buy the mons)
Suggestions:
1. It was removed for a reason, because people kept accidentally breeding their shinies with normal mons
2. Shiny brace to guarantee the egg would be shiny would cost a ton imo, and would prevent the egg to gain stats unless there is some kind of an increased highroll chance or something
3. I don't think there is an increased highroll for ivs, but if you took that out it would make shinybreeding a moneysink, because eggivs would change but not increase
"effects":
1. HOW? If you made shiny breeding guaranteed shiny eggs with normal parent the shiny prices would go way down, because you only need 1 shiny and there just breed it into a comp lmao
2. how is that a negative when you want more accesible shiny comps?
Conclusion:
You are making this suggestion to lower the prices of breeding a shiny comp which in fact is the same prices as breeding a normal comp but paying millions for mons. But this "issue" doesnt come from breeding costing a lot, it comes from shinies costing a lot. You saying that "hey these changes make shiny breeding cheaper" whilst saying that "it would be still much more than a normal breeding" is basicly shooting yourself in the foot, because you don't know what makes shiny breeding expensive and you don't convince me that it would lower the prices. Also the line "you can only pass a nature/iv per breeding" shows me you don't have knowledge in breeding in general. Because how comp breeding works is that they pass 1 iv and nature or 2 ivs to the egg and advance guaranteed. Your suggested shiny breeding method would cause scenarios where you breed a nature onto a shiny, then losing the nature because you bred on an iv, then losing an iv because you bred on a nature and so on, making shiny comps basicly impossible to make and making shiny breeding in general a money sink. That's why this suggestion is stupid.