If you have customization you don’t want to bring forward, you need a “clean start”, have significantly changed the way you do business, our have unsupported ISV’s, A reimplementing might make the most sense.
Migrating your data using the Microsoft toolset is the generally recommended path if you have many customizations, and master data, pending invoices etc. you want to bring forward into your new ERP system. Remember migrating data can be a significant task. We offer an expert evaluation of your option from a cost, time and clean data perspective.
If you need your code and data in their entirety, you could double upgrade. First to AX 2012 R3, then to Dynamics 365 for Finance and Operations, Enterprise Edition. This could give you a potentially more complete set of code and data.