Get familiar with USERRA protections if not already. I had a gig at an airline throwing bags paying my way through school. Told Mgmt i’m entering active duty, they said send my EAD orders to HR, they collected my badge and sent me off no questions asked. I also sent a copy of orders to my union too for record.
Been out 5.5 years and still have my position if i choose to go back. Still have flight benefits, been able to add my wife and kids to them as the years went on, it’s been pretty sweet. Word on the street is i still have my locker in our break room still too haha.
If anything i’d suggest a place with a large workforce that will have the manpower to cover your loss should you end up on 6 month orders short notice...that is if u care. If u dont, any company that supports your lifestyle between orders works in my experiences.
For insight into the “professional” companies, had a mentor working for Berkshire Hathaway doing “professional” type things. He was on orders for like 4 years, BH did away with his former position and made a new one for him when his orders ended...then he ended up on long term orders again soon after he went back.