Emergency fund is needed only after starting investment, that is why emergency fund is needed where you can continue investing Bitcoin regularly on a weekly basis. Investing Bitcoin according to the DCA method will allow you to buy Bitcoin regularly and you will also be able to hold it for a long time.
If you spend time in illness, then you may refrain from investing because you may not have money saved, then you can invest Bitcoin from emergency fund. Regular DCA method will be followed to deal with danger and to sustain Bitcoin investment for a long time.
Your advice is good, but when someone invests in DCA method, he has to take a long term plan like he will continue the investment for the next 10 years and then he will think about the profit (this is my personal opinion).
Now if someone thinks that he will manage the investment for only 1 year and then he will make a good profit from it, then good results may not come. So in this case, long term planning is important.
At first you can’t build bitcoin stash in one year , it may definitely takes long for one to build a better stash it all boils down to how aggressive one trend to be with his investment.
In my opinion dca is just the best and is not for those that are not too financially stable , even those that are financially stable can make use of it , for instance you have the amount to buy 2 bitcoin (and that is your target goal ) I will advice you to spread the purchasing with dcaing rather than using lumpsuming , because you be able to purchase at different price interval .
Using both just the best you can start with lumpsum and continues with dcaing to keep buying at different rate either or low .