In my opinion, the responsible thing to do would be to do it on testnet. Intentionally forking the mainnet block chain knowing it will likely cost some people money is a pretty crappy thing to do.
First of all, I don't think they are many people who do not rely on bitcoin core professionally. Some run a different implementation for personal use but when money is at stake the risk of loss is too high.
There are several large companies, such as Coinbase, that don't run on Bitcoin Core.
Even if it is a small bug that makes you miss a transaction, it could be a very large transaction that ends up costing you your business.
The transaction will end up in the block chain anyways (short of a massive network-wide chain fork that reorgs your transaction out and it got double-spent, but that is an issue that applies across the board regardless of any bugs), so even if your implementation didn't see it for some reason, the transaction, and hence your money, isn't lost. The only time I can think of where this wouldn't be the case is if the bug involved sending the transaction to the wrong address.