Travel Expenses for Greece

Hi all,
I'm hoping to get some help regarding the "standard" of reimbursements for international travel, when someone works and is a citizen of Greece. Here are the details...

We have an office in Ann Arbor, MI USA and one in Athens, Greece. We are sending multiple people from Athens to China on a business trip.

Our employees in Greece are asking to be paid upfront for their luggage cost (something I can't do as per the Chinese airline, they must have their baggage weighted and pay there)

They are asking to be reimbursed for additional expenses they they will have during a 12 hour layover (accommodations and food will be reimbursed already)

And they want to be receive the money in advance for their VISA expenses.

Are there other business expenses in regards to travel I should be aware of for Greece?

I know how things would be handled in the USA. But I'm hoping someone or multiple people can help with how they might be handled in other countries.

Thanks!