I have been watching Supergirl since it came out. It's certainly not the perfect show but it has been worth watching. This isn't a review though it's a single point of one thing that need to happen on the show soon.
At the beginning of every episode you have a voice over explaining who Supergirl is. It's not as good as the voice over on The Flash but it's worth having so people can jump in. One of the primary points in that voice over is that she was sent to earth to protect her cousin, but she went off course and by the time she arrived he was Superman and the implication is fairly obvious that he doesn't need her protection but everyone else does so she takes up his cause of protecting everyone else. A good cause, and one that makes for an interesting show, but she still had a mission.
That is where my point comes in. At some point, preferably sooner than later she needs to fulfill the job she was sent to earth to do. That is to protect Superman.
The first step of course is that they need to cast Superman. But they don't need to have Superman on the show. They need to have Clark Kent on the show. There is no good reason that they couldn't or shouldn't have Lois and Clark come visit the city and Jimmy Olson. It would be fun to see without having to have him do anything super. Ideally you'd have Cat Grant invite Jimmy, Clark, Lois and of course Kara to some sort of event or meal. This way they could interact but not have the obvious conversations because there is someone who isn't in on the secret there.
But primarily this episode is setup. A few episodes later you have Superman be weakened in some way. It doesn't really matter how, but I'd have someone steal his powers. So now they have the powers of Superman and Clark doesn't. Kara learns about this, either from the news of from Jimmy. Metropolis needs help and perhaps more important Superman needs protected because if he dies the person who stole his powers will keep them forever.
The problem of course is that Superman is as strong as Kara and the man who took his powers knows all their weaknesses and is willing to use them and more than happy to kill Kara. Everyone, including Clark, tells her that she shouldn't fight him because he's too strong, but she explains that she wasn't sent to Earth to protect it or to live a normal life. She was sent to the Earth to protect her cousin and that's what she is going to do. Besides, the world needs Superman.
Once the fight starts it's clear that she can't win. He's stronger than she is and a better fighter, but she doesn't stop. They exchange blows that would kill anyone else and in the end Kara finds some way to stop him, but is badly wounded in the process. She is going to die but because she defeated the villain Superman gets his powers back. He flies in and carries her to the Fortress of Solitude (or close enough to the sun to heal her). She of course lives and she and for the first time in the show you see Superman and Supergirl really together.
There are a few reasons that this is important. The first is that DC or whoever is making the decision needs to get over the idea that you can't have a Superman/Batman, ect both in the movies and on TV. It's silly. The argument that it might confuse audiences is stupid because if anything it's far more confusing to have Superman not appear on the show. Does that mean that it's supposed to bet he same Superman as in the movies? Is it the Superman from Smallville? Or is it simply a different superman. One we haven't seen before. Whatever the case you can't clear that up until he's on the show.
Of course the real reason isn't confusion. The problem is that they are afraid, and possibly rightly so, that the Superman that is on Supergirl will be better than the one in their movies. I'd suggest making better movies, but I'm sure their doing their best so I'll just say get over it. Does anyone really think that having a good flash on TV is going to make people want to see The Flash in the movies less, or is it more likely that having a character they already know and care about will make it easier to convince them to see other things that he is in. The same is true of any other characters.
The reason the show needs to do it though is that they need to show that she is Superman's equal. In the scenario I suggest she not only beats someone who has Superman's powers, but someone who has beat him. And beyond that she stands up to Superman to do it defying what he tells her to do because she thinks it's the right thing to do. I might even add a line from Lois pointing out that risking her life to protect him is the exact sort of thing he would do.
Finally, since all of this is seen by the whole world you no longer have to have Supergirl proving herself. She can afford to have Superman or anyone else help when she needs it, but also make her powerful enough that she isn't likely to need it ofter. In this way you can have Superman show up once or twice a season to help with something, or even better to ask for help.
I understand that there are likely people being told they can't do this and I don't know their plans for the show in the future, but I really believe that having her actually do what she was sent to Earth to do, protect her cousin, is a great way to make the character and the show a bit more interesting without having to make major changes to it.