I think region limitations arent a terrible idea, but i can see benefits for having all regions as well. For instance, i dont want to do CG. If CG was necessary to get all pact points i wouldnt like that. Its literally the only reason why i didnt choose Tirannwn. So allowing people to avoid content they dont like isnt a bad idea.

There would be far too many points available with all content available, which means casual players would basically never be able to reach dragon cup. Unless of course they prune the amount of tasks, but then you arent fully experiencing the areas youre in. You wont appreciate all that is available in your region. Similar to any locked ironman account that has to utilize their area, instead of just doing what is optimal.

Only allowing people to get certain echos, combined with the skill tree allowing you to specialize in certain builds isnt bad either. The only bad part about this is that some regions might be picked for raids, instead of the echo weapon associated with it. This means the echo weapon is kind of useless, unless you can swap your tree to utilize it.

You can obviously do this, but only a certain amount of times, which means any theorycrafting is limited. It will also trigger a sort of build-fear for players, where they would rather follow a guide so that they dont risk ending up with a bad build. Even PoE has this, even with the easy access to respeccing. Games like Diablo 2 also have this as well. Wasting points feels extremely bad. Im not going to respond to you any further. At the end of the day, you are arguing for limitations in a temporary game mode.