How to derive a private/public keypair from a random seed?
How to derive a private/public keyset from a random seed?

In principle: seed a Cryptographically Strong Pseudo Random Number Generator with the random seed, and use it to generate the RSA key pair &quot;normally&quot;. For the later, we could use FIPS 186-4 B.3.2.

Are there major security flaws with this approach?

Yes, the obvious one: any entity knowing the seed can compute the private key. We need to trust every such entity beyond the designated holder of the private key to only use the seed to compute the public key.
As an aside, deterministic RSA key pair generation may need extra work to be protected from side-channel attacks (timing, power analysis).
There's also a functional issue: RSA key generation is rather slow, and implementations often have no firm stated upper bound on their execution time.