It's definitely possible to write simple EDI transactions (no HL loops, etc) with a couple of trading partners using something akin to mustache templates – many of our customers come to us after getting something basic like this up and running in a day or two, and then hitting complexity.
It's difficult to use the method you're describing to write a transaction like this, particularly when the receiver's system can fall over due to a single character out of place: https://www.verizon.com/business/support/vec/onlinehelp/dam/...
(I'm the CEO of Stedi)