Buildable end portals to more easily access end bases.

In order to make bases in the end more realistically feasible, so that one does not need to travel great distances through the end from the existing portal, we should have buildable and portals that transfer between the end and either the nether or the overworld in a similar manner to how nether portals connect to the overworld with some ratio that changes travel distances. These portals should be constructible only with materials that you must be in the end to get to prevent them from being built before the ender dragon is killed. I suggest purpur blocks instead of obsidian, and otherwise working just like a nether portal, to connect the end to the overworld or nether. Or perhaps some different designs to allow nether to end portals and overworld to end portals, always incorporating a renewable block found only in the end so that we can't cheat and build them until we've accessed the end through the traditional portals. This would make the end much more usable for building farming and basically making it more a part of Minecraft and it would be very easy to implement.