The features that enables BLE long range is currently not supported by the ANT protocol, I don't know if this is something they will add, you could try to ask on the ANT forums.
We currently don't have any ANT SoftDevices that supports nRF52840, but if we did I guess you would be able to use the higher output power available in the chipset. If you want more information about this you should contact the regional sales manager for your area, if you don't know who it is, send me a PM with your location, and I'll let you know.
