The simple answer is to NOT go 1511 if you want to keep the logistics processes un touched.
S/4HANA Finance (1503) is due an upgrade so you could look at that version.
However it is worth noting 1503 does not use the S4CORE component that you get in 1511.
The level of change within 1511 is much more dramatic than moving to S/4HANA Finance.
I would suggest you work with SAP or your Partner to help you decide the correct version that you move to, and the scope that you utilize