The rotating "grip-shifter" can be replaced with a "trigger-shift" with the same number of speeds (Shimano, of course). I did this on one of my folding bikes that had a grip-shift which was hard to shift wearing heavy gloves (it's my "winter" bike). The hub is a Nexus 8-speed, and the trigger-shifter is Alfine. I just went out to my garage and checked... the Nexus hub is "low-normal", and the display shows the correct gear. I have another bike with an Alfine 11-speed hub. This is a "high-normal" hub, and the Alfine gear display is reversed compared to the one on the other bike.
Bottom line: if you get a trigger-shifter that's Alfine vs Nexus, the worst thing that's likely to happen is that the gear indicator will read backwards. There may be a way to reverse it... I don't know.