This is almost exactly the opposite of what most new airlines do. The fastest, cheapest way to get a good plane is to buy an old plane from an existing airline (preferably one going out of business, so you get a deal) and renovate it a little.
Ryanair is the best performing budget airline in Europe and they only buy new planes, because it's way cheaper to run them. Less time on land for maintenance = less wasted money.
Ryanair was founded more than 40 years ago. An established budget airline choosing to strategically make an expensive choice isn't the same as a new airline starting up.
Used, high quality machinery is always in demand, but I think "used" and "planes" have the ability to subconciously sow some doubts in many people. I personally never heard of any airlines with 100% used planes in their fleets. I definitely would choose an airline with 100% new planes. I guess I'm another victim of marketing.
The 737 MAX is fine enough. But it's not like you can order those for immediate delivery either. There's almost 5,000 pending orders, and Boeing can make on the order of 500 of them in a good year.