It'd be a situation where you would play 5 bowlers. There are plenty of examples of allrounders who wouldn't make the team solely as a batsman but batted top 7 because they had enough batting talent and their bowling added balance to the team.
As I said, I personally prefer India with 7 batsman as I think its their strength, so I'd drop a bowler for Kapil Dev, but dropping Raina (which looked a lot more reasonable before the WI tour and day 5 of the Lord's test) for Kapil Dev would hardly be the worst move. It'd strengthen the often criticised Indian bowling line-up, and Dev is hardly a mug with the bat. You can't say Kapil Dev's batting is that much worse than Raina, Yuvraj, Pujara etc. who have played for this Indian team in recent years.