It might sound silly but the connectivity aspect of an integration can turn out to be the trickiest as I have seen developments delayed due to misunderstandings.
Comms is a bespoke skill set
Over the years I have implemented various connections. With each connection a different team is involved as the connection has it's own unique trait.
If you do not have the internal skill set to manage this level of connectivity then you need to seek out the experts. This then comes back to your strategy and how you want to trade - please see https://www.southwestdataintegration.co.uk/post/how-to-get-the-most-out-of-an-edi-development
But what about FTP?
I have not mentioned File Transfer Protocol (FTP) as this will cause you GDPR issues if you are moving personal data around your network. Secure File Transfer Protocol (sFTP) is GDPR compliant and this can be enhanced if any sFTP connection is then whitelisted so only those connected systems can use that connection.