Would it be possible to make a mod that makes all your companions like you or dislike you 100%?
When you say like you, do you just mean to like, or would you want for them to romance you, regardless of sex?
If you just want to make them like you, use the console (a link was posted in a previous reply that will net you a mod that will show text typed in the console) to raise the flags. The console is invisible by default even when you type. Go to this Link as it has the list for all of the commands (the one you would want is runscript zz_add_approval) plus the numerical attribute in the console representing each playable member.
For example, if you want for Morrigan to like you more, you would type after hitting the tilde (~) key (no quotes and put spaces as shown) "runscript zz_app_addproval 3 25". 3 is the number for Morrigan and 25 is how much you raise her favor of you. Conversely, going negative will have her dislike you more.