Please define viable solution. It's like a piece of string: how long is it? It's a very subjective statement "6 weeks to find a viable solution" - could just as well be 6 months.

Sure you can deliver something that might seem viable and the customer might also a cycle of updates as the viable solution becomes the solution - but how many updates are tolerated and how bad are the problems in the seventh week?

Sure we dumped waterfall for agile and now we live in a constantly updating world of "viable solutions" ...