Which one is better for keeping further studies as an option, an IPM at IIM Indore or a B.Stat at ISI?

Both the above-mentioned options are excellent to be considered. The IIMs prepares you to manage people and processes, whereas the ISI prepares you to be excellent quants.

Many IIM graduates work as quantitative analysts, they get the highest-paying jobs. If the ISI course is more appropriate, you could take the Bachelor of Statistics course. Quantitative analysts, on the other hand, tend to wear out soon, due to heavy workload.

An IIM education provides you with a broad perspective on management as well as access to a large alumni network. So, if you want to work your way up the corporate ladder, an IIM would be a better option. At the end of the day, it's up to you to decide where your priorities lie.