You might try the first few tutorials for scripting, they cover how to do message boxes, properties, etc. I don't know what you mean by a fake keyboard, but messageboxes don't require SKSE.
Sorry...I have already read that, but:
1) Message Box have 10 button limit.
2) Message Box seem to work in a sequential way (so seems that you cannot have two message box open at the same time).
3) I might be able to make a fake Keyboard by staking more letters on a single button, changing with each button click, but then the act of inputing would be a daunting task...
I think he means something similar to the filter box from SkyUI.
Yes. I need a fillable textbox like that (or like the naming textbox at character creation).
I won't be able to help (I'm no real good with any scripting) but maybe you should mention what you want to achieve. I've had help that way, different solutions to reach the same goal.
The idea is to create a general script which renames something with a name chosen by the player...but I need to have an usable textbox to do that.

Thanks,
Jashkar