Sure, there are some felons who are truly reformed. But, if there is a good way to make that determination, I'm unaware of it. I sure don't want some Democrat governor deciding all felons are good to vote (as happened here some years ago).
How about felon gun ownership after they are out of prison?
The Constitution specifically makes provision for denying criminals the right to vote but, none to infringe on one's right to keep and bear arms.