Create tracker from scratch or customize existing open sourced solution?

[mediaid]

It's now necessary for us to get some customization to our current tracking that's not possible in any existing products. We need to integrate the tracker with other data aggregation sources so we need something else than what's already on the market. We have started to look for a development team for a new custom solution but we're also considering if it could make sense to customize an existing tracker where the developers would license out an open sourced version.
We would like to chat with someone with experience developing such an advanced piece of software about the pros/cons about our possibilities.

Thanks!!