Customize Typescript compiler output

I need some help getting started in customizing the compiler output of typescript, or to be more precise if it is even possible.

I have the openui5 framework, which syntax, for example extending classes, varies strongly from ES5+ standards. Also AMD works differently.

Here is an example:

I would like to import a module. In typescript it should be:

import { Button } from "sap/m/Button";

which puts out something like this in javascript:

var Button = require("sap/m/Button");

But what I need here is:

var Button = sap.ui.require("sap/m/Button");

Another example:

Properties are resolved with getter and setter functions. So when you extend a class you can give it a json object with properties:

properties: {
   "title" : "string",                         // a simple string property, default value is undefined
   "buttonText" : {defaultValue: "Search"},    // when no type is given, the type is string
   "showLogoutButton" : {type : "boolean", defaultValue : true},   // a boolean property where a default value is given
   "width" : {type : "sap.ui.core.CSSSize", defaultValue : "50px"} // a CSS size property where a default value is given
}

now openui5 will take the given property and generate the setters. For example for the "title" property the two functions will be generated:

getTitle();
setTitle(value);

But no ES 5 property.

So in typescript you cannot access your property like this:

let myclass = new MyClass(); myclass.title = "Hello World";

but you will have to use the getter and setter methods:

let myclass = new MyClass(); myclass.setTitle("Hello World");

What I would like to do here is to write this typescript code:

let myclass = new MyClass();
myclass.title = "Hello World";

which transpiles to this javascript code:

let myclass = new MyClass();
myclass.setTitle("Hello World");

I think I can do this on my classes using decorators, but you cannot use decorators in declaration files (d.ts). So I cannot use the base classes this way.

So here is my question:

Is it possible to extend the typescript transpiler and tell it to compile this stuff differently?

A push in the right direction would be much appreciated.