Can I drop one year for the IPMAT (IIM Indore)?

It is a risky option to drop a year for IPMAT because the acceptance rate is extremely low i.e. 0.7%. It would be better to keep other options as a backup in place.

You can start studying for other entrances as well or get enrolled for a course if you want to save a year. You can also leave and go for IPM a year later if you get selected. 

But, if you think that you are very serious about IPM, and you will do whatever it takes to get on by preparing rigorously after taking a drop for a year, and if you have a strong belief that you will get into it, then consider taking a drop.