With BWoH you can do several things differently, in particular you can eliminate several persistence layers on your BW model (according to the LSA++ principles), for example you can eliminate the PSAs and load directly into an aDSO (advanced DSO, BW 7.4+) and you can also eliminate the cubes and create virtual models with Composite Providers on top of your aDSOs and infoObjects.
Regarding the extraction, you can use alternatives such as SLT to load data from ERP into (BW on) HANA without using the standard ABAP extractors. On the long run, when you have your ERP system on HANA (S4), for all the operational reports, you don't even need to extract anymore, having your reports running online of top of virtual models (calculation views in HANA) created on top of the ERP transactional tables.