I don't think the extra transaction fee of Bitcoin should be a deterrent to your investing in DCA method. Now we are regularly noticing extra transaction fees for Bitcoin and you can use a good quality exchange to avoid this extra transaction fee problem. As per the current situation for investing I would suggest you to use Binance Exchange. Since you are investing according to the DCA method, when you feel that you should increase your investment now, you will deposit your country's local currency in Binance and after depositing, you can directly purchase bitcoins through p2p transactions. Or you can buy virtual dollars and later buy bitcoins with those dollars. 

Additional transaction fees are not a big issue for those who want to hold their investments for a long time and who want to invest in Bitcoin considering the different phases of the Bitcoin market. Our willpower is the most important, if we have the willpower to invest then surely our alternative thoughts will come to our mind. It is now a bit difficult for those investors who transfer their investments from mobile wallets to exchange wallets. In the future when the transaction fees are normalized, an investor can easily transfer his investment from exchange to hardware wallet or software wallet, it is not a difficult task.