An internal browser is a good idea, but in the interim, this problem can be solved by changing your default browser/app settings. You should be able to make it so that any link automatically opens in Firefox, or make it so that clicking on YouTube links prompts you to select which app you'd like to open the link with. Not sure what type of device you're working with, but on Android you can change these settings by going to Settings > Apps > (insert app name here) and looking under the "Defaults" header.
An internal browser is a good idea, but in the interim, this problem can be solved by changing your default browser/app settings. You should be able to make it so that any link automatically opens in Firefox, or make it so that clicking on YouTube links prompts you to select which app you'd like to open the link with. Not sure what type of device you're working with, but on Android you can change these settings by going to Settings > Apps > (insert app name here) and looking under the "Defaults" header.