Questions related to the Teambuilder!

So when i queue into the teambuilder as captain,after selecting my champion, position and role, i click on find solo players and then i specify what role i want in each position.

As well all know we can only select only "One role" for "Each" position. For example, I select Postion as "Middle Lane", then for role i can only select either "Assassin" or "Mage" but not both. Why is that? I'd happy if i get either an assassin or a mage. But Teambuilder only lets you select "One role" for "Each" position. These tends to sometimes increase the time it takes to fill a certain role.

My 2nd question is as captain after you select all the details of the position and role and hit the search bar, why can't you pause the search and change some of the things. Like for example, it was taking a really long time for us to fill the postion "Jungler" whose role i specified as "Fighter". One of the players who had joined me in the teambuilder lobby, said that i should have given "Tank" in the role for the position "Jungler" to find people faster. And so i tried to change the role from "Fighter" to "Tank" but teambuilder doesn't allow that yet.

So yeah if someone from the teambuilder team could answer my questions it would be really nice! :)