I think you need to be very careful here. Covered calls don't reduce risk or increase performance overall. If they did, every investment manager would be using them. In a typical portfolio, over the long term, the gains you give up when your stock goes beyond the strike of your calls will negate the premiums you receive over time. Psychologically, covered calls are appealing because your gains happen over a long period and this is why many people suggest it. But if you believe the Black-Scholes model (used for pricing options) this is what the model predicts over the long term - that you won't do any better than just holding stock (unless you have some edge other traders don't).
Now you say you want to reduce diversification and raise your risk. Keeping in mind that there is no free lunch, there are several ways to reduce your risk but they all come at a price. For simplicity, there are three elements to consider - risk, potential gain and cash. These are tradeoffs and you can't simultaneously make them all favorable. You must trade one or more of them to gain in the others. Let's say you wanted to concentrate into a few stocks... how could you counteract the additional risk?
1) Covered calls: very popular strategy usually intended (erroneously) for increasing returns. You get the bonus of cash along with marginally less risk. But you give up a substantial amount of potential return. You won't have blowout returns if you do this. You still face substantial risk.
2) Collar your stock: You sell a covered call while using the cash from the sale to buy puts for protection. You give up potential gains, you're neutral on cash but gain significantly on reducing risk.
3) Use calls as proxy for stock: You don't hold stock but only calls in equivalent delta to the stock you would have held. Substantially lower risk while still having potential gain. Your tradeoff is the cash you have to pay for the calls. When using this, one must be very, very careful not to overleverage.
4) Puts as protection for stocks: This is basically the same as #3 in tradeoffs. You won't overleverage and you also get dividends. But for the most part it's the same.
These are the main ways to reduce the risk you gain by concentrating. Options themselves are far broader. But keep in mind that there is no free money. All these techniques involve tradeoffs that you have to be aware of.