I am 100% against this. Not because of Chris Pratt, I think he could be okay in the role.

I'm against it because Indiana Jones should not be rebooted. It is the action adventure franchise, beyond iconic both in cinematic history and just in pop culture. To do away with all that is ludicrous.
I would be completely behind starting up a new adventure series with a new character that is obviously 'supposed' to be Indy, but isn't officially declared him. That would be awesome. But an Indy reboot: no.
I could even get behind putting Chris Pratt in as Indy in the established world and continuing the adventures that way. It would be odd not seeing Harrison Ford, but at least the franchise stays intact.
So to be clear, I'm not against expanding Indiana Jones' adventures. The more the better I say, that's why Indy is the greatest, because he has done everything. What I will not support is erasing the already formed stories in order to start fresh.
I'm assuming the reason Disney is considering this is because they want to take Indy to a different era? That would be the only thing that would necessitate a reboot as opposed to simply recasting in order to go back in the timeline.