what would India have been like if it had not been invaded in the mediaeval period
Answers
For worse or good, India is only because of all the invasions and migrations. You wouldn't be who you are and where you are if not for all these sequence of events. Taking away couple of events doesn't always mean good. It is just make things different. If no Mughals and British invaded then it would be little better than today in some factors but India as a single nation wouldn't have been possible. Even in the best case only 60 to 70% of our current land mass might be India or with some other name but definitely not the whole. The probability of that one huge nation(Mauryas, Guptas or Cholas) with 70% land mass to happen right at the beginning of 20th century(Borders were defined) is very less. So on any day I would bet my money for multiple small nations with the size as small as Bhutan or little bigger as Pakistan or Afghanistan. It is not that I don't believe we Indians never thought of getting united as one nations but chances of one huge kingdom right at the 20th century is less.