Yes, it is certainly possible, but no it isn't necessarily easy. I'm not going to write this for you, but I will explain to you what has to happen.
The first thing that has to happen is, of course, the window has to be created. You'll have to look at the Scene_Input to see how they initialize their windows. Then, if you look in the update method of Scene_Input, you'll see that they call an update method for each window. Likewise, we have to update the windows. You would have to put the update methods for the windows in the update loop of the Scene_Map.
Now, the only caveat is that this Scene_Map now is trying to do 3 things at once that shouldn't happen at once. It's handling all of the processes of the map you don't control (events, weather, etc.) which is good, you want it to do that. The other 2 things it does are the problem. It is processing the update window and updating the player. You only want it to do one at a time.
The other problem is that you'll see that the input windows are always over the map. What you have to do is make a sort of switch to control when you are doing input and when you are doing player walking and such. When the player should be walking, set the visibility of the windows to false and make neither window active. When the input should be working, don't update the player and make the windows visible and set the proper window to active. Then you also have to make sure that when it switches from input back to player, it changes the player name in question. (or whatever you are handling input for.)
What you want to do can be done, I have done it before myself. I just can't access the harddrive on which I stored it because it's for a laptop I no longer can use.
If none of this made sense to you, then just wait until someone comes who can do this for you ^^
