The One-Minute Wall
As a musical idea or starting point for a song, I really like it. The challenge now is to build out the song.
At the moment, your core idea consists of a catchy 10-second, 4-measure phrase. After the 2-second intro, you repeat the phrase 7 times. During the first 3 passes through the phrase, you do a great job of adding layers. The next 3 passes sound very much like the third pass, which gets a bit repetitious. In the seventh pass you drop out the vocals, which is a very effective change of pace.
At this point, you've hit the "one-minute wall". You'll need to introduce a new theme in order to continue forward. The second theme should not repeat the same chord sequence as your first theme. A major challenge of song-writing is come up with additional themes that complement your first theme, in order to build the song out to it full length.
The second challenge is to choose an effective organizational structure for the themes or melodies. However, in my opinion, the first challenge (creating complementary themes) is much harder. You've got theme "A", but what will you use for "B"? And you'll probably need a "C" theme, perhaps to serve as a bridge at around the 2-minute point.