What are the ways to minimize traffic loss when the site crashes and downtime?

Question

css

I work as a project manager.
An uncontrolled traffic growth of 30 times is planned for the project.
Traffic is expensive, we don't want to lose it, if suddenly we can't stand it.
The team's suggestion is to wait for the site to go down and take action.
Estimated downtime will be from an hour to a day.
I had a suggestion - to control traffic. 
If there is a problem with the load on the server, the site returns part of the pages correctly, requests in excess of the specified rate return 50x errors. The site will not fall down and will continue to work at the maximum of its capabilities. And we will calmly fix problems on the server: install servers, fix configs, etc.

The advantage of this solution is that we save a maximum of money, and there is no need to restart the servers completely, i.e. downtime will be reduced to zero. 
The team is against such a decision, as they believe that we will not see the cause of the problem until the site goes down.
What will the community say? What other solutions to the problem of maintaining traffic in a situation of such growth of great growth?

Answer 1

bradsknutson.com/blog/css-sliding-underline
here is the solution, maybe it will come in handy for someone

Answer 2

like this tobiasahlin.com/blog/css-trick-animating-link-unde...

Answer 3

What prevents you from conducting preliminary load testing (such as DDOS yourself) and seeing the maximum possible load and possible bottlenecks? Another thing is that the team may be too lazy to do it?
Or maybe they just don’t believe in marketing, they don’t believe that they will be able to attract so much traffic.

Answer 4

why do you need 30 times traffic if you can't digest it?