..Or rather if you were to make  a 2D RPG engine  similar to RPG maker  what would you  add that it doesn't have , what would you change about it , or  what would you do differently?   For those that use it what about it don't you  like or what about it would you change?

RPGmaker isn't terrible although I admit there hasn't been much  added since script support.  C# is a nice added feature and I know the previous iteration had LUA but in my mind the best is still the first RM2K, complete with Don Miguel's shaky translation.

The features I would like to have seen implemented since then are mainly for the art.  If I want to change a specific tile character feature or mix and match tile and sprite sets I would like to be able to do so in the editor rather than having to do it in outside software and import the results in.  I like the way they handle sprites, tiles and rooms in Gamemaker Studio 2 and wish they would implement something similar in RM, no limitation on layers and the ability to generate assets within the engine instead of a bunch of ugly preloaded stock assets.  I haven't liked the RTP artwork since 2k.   GMS2 room, level and and sprite editor paired with RM or RM like options to replace the drag and drop and still supported direct coding, that's the engine I would make if I was capable.

I  will have  full support for all of that!! I can't believe  RPG maker doesn't support simple things like  drag and  drop or custom tile sets in editor .  But I have used  RPG maker I just downloaded a trial version on my wincrap computer.  I'm a Mac guy and they have no mac trail :(.   My map editor will look some what similar to tiled  but, with support for animated tiles  and changing tiles ( tiles that change with tile temp / rain fall /  season/ adjoining tile textures ECT.)   as I have used that one  and found it be  easy to use  and flexible.