I have an idea for a unity app which goes like this, Let's understand it better through an example :
Suppose that I wanted to create a racing game. I have the models of the car, road, lighting etc. in an assets folder. I would open the unity app and I would be able to basically drag and drop these components from a side panel which reads my assets folder into a scene and edit the scripts attached to these components.
As a user I should be able to change some functions of the components in any programming language that I want (Let's also assume that the editor in the app will support Intellisense/Intellicode) but, the basic features of the car, road, physics will be defined by us in a different program (Lets say unity itself) and that can be modified using an inspector window. So, the main purpose of the app is to just implement the game logic. As a user of this app, I am not worried about anything other than the game logic. It is in essence a very lite version of unity.
Maybe the example of a racing game is too complex for such an app but let us say maybe a robot that can be dragged and dropped from the side panel and we can edit basic features like height, width, joints etc. from an inspector like panel and also add some features to the robot like move arm from x to y in z seconds using python or any language of choice?
The immediate question that you may, as a reader will have is why not use unity itself as it provides all the features mentioned and more. But, that is where the problem lies and this app is catered to a very niche group of people who have never used a sophisticated software like unity before. Yes, it would still be easier to learn unity and implement a game/app like this but I want my niche group of people to only worry about domain specific knowledge and not worry about advanced programming patterns.
Is it possible to create such an app from unity which will allow these requirements? If not, as an expert, if you were given such a requirement, how would you go about it?
That sounds a lot like a program like Game Maker Studio.
Unity (like any other game engine) is not built to make such complex multipurpose programs (that doesn't mean you can't do it, but it will lack in performance and it will be really bloated), but for a big project like that I think you should design and build it from scratch, possibly in a fast language like C/C++, since a program like that has to be as fast as possible.
There's a reason why every game engine is written in C++, and not built on top of an already existing engine, they are made for an entirely different purpose.
If you need a starting point on YouTube is full of tutorials on how to create a game engine from scratch, this may be a starting point.
Just make sure to plan everything ahead and have a well thought, written down idea of everything you want to do :)