Don’t think so as long as you’re able to flash /e/OS back (which is normally quite easy).
But I’m not sure VoWifi or VoLTE will work in US with other ROMs.
Anyway A13 /e/OS for FP4 should not take too long anymore as Beta is already running quite well. And one features I like is that - as for other LOS based A13 ROMs - there’s finally a charging limit configurable now. 
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