On gmod there is an addon called Tardis Rewrite and in that mod you can actually directly walk into the tardis without being obviously teleported. In the most popular Tardis Mod you get transported to a new dimension and it kinda messes up the feel ya know? So i would like a tardis mod that allows you to walk into the tardis without all the extra. You should be able to see from the outside that it is bigger on the inside.
I am actually currently working on a mod that would do exactly this. It is not however limited to a Tardis. The way the mod will work is that rather than minecraft being in 3 spatial dimensions, it will be in 4. It is really complicated so far and requires I have to completely rewrite A LOT of code and make the completely change the rendering so that I can render through dimensions, almost like in Portal. I don't think i'm going to have this done for a LONG time (like a few years, because I don't completely understand how all of minecraft's code works. If I did this would be a lot easier) but it's a project that I have been wanting to complete for years so hopefully I'll have it done eventually.