Separate module for custom backend code and UI

[gauravjlj]

I want to use ofbiz as an online eCommerce store at least for the now but UI 
seems very old and can't fit in today's time.
So,
I would be having many changing in business logic in backend/frontend and I 
don't want to change the existing logic rather I want to build a top layer 
which will include my new UI and custom backend code, So out of the box code 
remains intact in that modular approach and also if any new release comes then 
it would be very easy to upgrade my system. Is that possible. We do the same 
thing in Oracle Commerce but I can't afford it :)