Glad you were able to upgrade the systems to Java8. It seems like the client didn't know that it matters and didn't have any strong opinions on the subject.
Clients often are unaware that they have relevant information, and don't seem to volunteer it easily.
If you haven't begun the work yet, and wish to see if your potential market can meet your software requirements, you need to do a bit of research. Engineering doesn't get to define what customers you can go after, that's the real job of a Marketing department and ideally begins long before Engineering has even thought about the problem. Engineering can certainly respond to Marketing with budgets and schedules.
I'm often forced into lame technical decisions so we can cast a wider net for compatibility with customer environments or to support a few obscure customer requirements because their business has been given a weight above what their initial orders might imply.
(note: I work in the silicon industry, it's tough to be agile there. Because some of our requirements get baked into hardware design about a year in advance of the SW work)