I am implementing a smart contract with some admin functions (used to change limits). I would like to require at least 3 out of 5 owners to approve any usage of this functions. Would you rather use GnosisSafe (more complex to use and costly, but already audited), or some simple implementation (super custom for this specific contract to make it simple to use and less expensive, but it would require an audit)? Or maybe reuse some governance contract like GovernorAlpha from Compound?
Welcome to the community
The cost of developing, appropriately testing and auditing a custom multisig is likely going to be greater than using an existing multisig such as GnosisSafe. So I would look at using an existing multisig if this meets your needs.
If you are adding governance, then you may want to collaborate on Contracts for Governance.
You may also want to look at: https://blog.openzeppelin.com/admin-accounts-and-multisigs/
I would recommend looking at using OpenZeppelin Defender for admin actions with multisigs: https://docs.openzeppelin.com/defender/admin#multi-signature-wallets
We do regular webinars on OpenZeppelin Defender, our next one is: Webinar: Introduction to OpenZeppelin Defender - Wednesday 31 March 2021
Do you know of any Multi-Sig solution compatible with Defender when working on Matic aka Polygon / Mumbai ?