The KAI T-50 is a supersonic trainer aircraft,meant for training purposes only.I dont really see a point in buying a trainer aircraft and then again modifying it to suit a full fledged fighter.The A-50 is a light attack aircraft and IAF has options for that role in its inventory
An Airforce builds up its inventory based on the immediate requirements.Analysis is not based upon some magically appearing aliens over the horizons.Thats where the comparison starts my friend..
A multirole fighter is a good idea and I dont doubt that,but at times we also need a dedicated system,because a dedicated system will be optimized for that particular role which will be its area of excellence.The idea is good enough.the cons part is u will have to maintain a lot of jets to do that.And I think the IAF has the capability as well as money to achieve that.
Redoing something is necessary when ur requirements change.The primary requirement for which LCA is needed is the necessity to replace the aging MiG-21 s.
Anyways systematic changes have been made in aerodynamics, electronics and engines to make it better.Obviously we will never get to know the trade secrets in its entirety,but some info about changes,and newer developments can be found here::
Link!!