Mac1986 (1/2/2013)
1) I see that Indexes have heavy fragmentation levels: This effects the DML Performance for sure, but will this allow the data file size to grow extra than actual consumed space?
NO there is no 'extra' or 'actual consumed' kind of thing in index fragmentation level. framentation happens due to page split whch is dependent on fill factor.
Mac1986 (1/2/2013)
(2) Will adding few indexes at appropriate places reduce the Data file to not pre capture so much disk space than actual consumed space.?
NO. index addition always cost you space/disk and it helps you to retrieve the data faster but slow down your DML operation
for more details see this link http://blogs.msdn.com/b/pamitt/archive/2010/12/23/notes-sql-server-index-fragmentation-types-and-solutions.aspx
-------Bhuvnesh----------
I work only to learn Sql Server...though my company pays me for getting their stuff done;-)