Mirrorless Full Frame jump

Hi I have been a Nikon user, currently have D7100 (DX) SLR.

Considering moving to Full Frame. Not just that, but to Mirrorless as well. The later because of its small form factor, and great reviews of new Sony lenses.

Problem: I have invested in Nikkor lenses and Flashes.

I am posting this on Sony forum, so I will hear a bias, but would like to get an opinion on considering Sony 7x vs Sony A6300 vs Nikon D750. I am not too excited about Nikon mirrorless products. Having a built in flash may or may not be an issue, but considering I am an amateur photographer doing mostly family photos, I may lean towards A6300. Nevertheless, the biggest question is whether it does even make any sense eBaying all the Nikon accessories and taking the dive.

Thank you.