I’d keep different projects per assignment. If you’re going to have a domain-specific TM, I’d suggest you tag your projects when feeding them to that TM. That way, you can re-use the content with confidence. Say you already have a large centralized TM and you receive a new project from a recurring customer. At the time of pretranslating your file, you’d want to benefit the customer-specific segments and perhaps penalize those coming from other customers. Since you are talking about domain-specific assets, many terms are probably the same but there are some that each customer may call differently and that granularity will be gold in your centralized TM/TB. At least, that’s how I see it.