It's not compulsory that you should invest aggressively only from your reserve funds, a bitcoin investor can invest aggressively directly from his discretionary income, the most important thing is that you don't over do it. This is one of the reasons why if you have started your bitcoin investment, you need to look for a way to increase your income by looking for a second means of income or going for a higher degree for promotion at work.
When you have increased your income, you have also increase your financial strength which will allow you invest aggressively with DCA. I prefer investing aggressively with my regular DCA than waiting for the dip to buy cheaper aggressively with my reserve funds. However, your level of aggressiveness depends on the size of your discretionary income. This is why a rich guy has a strong financial strength to invest aggressively than someone who isn't rich.
Your emergency funds is to take care of real life problems and if you invest with your basic needs or your emergency funds, you are gambling
Investing aggressively with your emergency funds is the easiest way to fail in bitcoin quest. Every bitcoin bought with part or all of the emergency funds is like an impurity in a jah of clean water, it spoils the entire jah of water. Your DCA approach is all encompassing, it can allow for little more aggressive buys especially when you are strictly following it.
Having a financial intelligence would let you understand that you should improve your investments as soon as your stable income increases. Also buying by DCA would allow you to invest all all time and not only in dips. Waiting for dips also is another way of not investing at all in bitcoin. You may not be able to save your discretionary income with discipline, so it's better to invest at all time. In all your investments, don't invest beyond your financial capacity permitted through your Discretionary income.