Wouldn't support the use of closed-source wallets for the reason that they are inherently dangerous, obscured chunks of potentially malicious code but the problem with addresses you described is not actually a bug but a feature. When you receive a payment, the address with that payment becomes hidden, so you wouldn't be able to further reuse it easily. You can still access the address in a special section called "Address book", but you will be better off if never use it again for payments. Wallet software if designed properly always tries to preserve your privacy, that is why it should generate a new address each time you receive a payment and also a new change address each time you send bitcoins to others. Ideally, you should never merge coins from different addresses to not reveal they are controlled by a single entity, you should practice coin control to achieve maximum possible privacy.