If I had resources similar to commercial math software companies (so I could hire hundreds of professional engineers), I would still do a mix of writing new cod

If I had resources similar to commercial math software companies (so I could hire hundreds of professional engineers), I would still do a mix of writing new code from scratch and using existing libraries. What would change is the mix. Also, I would identify components of Sage of questionable quality/design, and put substantial resources into improving them (thus giving back to their communities). For example, Jakob Kroeker has been frequently posting on the Sage development mailing list about how he was -- out of interest -- systematically auditing code in Singular, and he found some serious bugs. Unfortunately, he is about to leave mathematics (since he's not going to get supported doing auditing?), but if I had more resources, I could hire him fulltime to systematically auditing open source mathematical software. It's a waste that such people systematically slip through the cracks, people who are passionate about auditing math software source code. The minute they start doing some of the things we really, really need, they vanish due to lack of money. After watching this for over 10 years, I'm starting to get really annoyed.