well, here's some perspective...I train in a very traditional kung fu method, under a sifu who has been training since the early 1950s. He's old-school, grew up in Hong Kong and trained with some heavies in our particular system. We've got a good number of forms in our system (I actually believe that forms are a very useful tool for training some very useful skills, tho they need to be taught properly, understood properly, and practiced properly and that often doesn't happen) and our training tends to place a heavy focus on forms.
Sifu has said for a long time, if you really understand your basics, and if you have only learned the first of our forms, you've got PLENTY to be able to fight with. If you've learned our 2nd and 3rd forms, then you've got enough for a lifetime of training. You really do not need the dozen or so other forms that we have, not to mention the dozen or more weapons forms.
But this hinges on what I stated: that you REALLY understand the stuff. Most people don't, and it takes time and work and correction before you do. Sifu has also said for a long time, that the forms really just teach us what is possible with the basics, how the basics can be used. They help us develop our vision for what is possible. IF you had a vision of what is possible, then the basics are all you need. But most of us need some help with that, so we learn more of the forms and that helps us develop that vision of what is possible. Eventually, more forms will not help you. If you haven't developed the vision with the forms that you've already learned, then learning more forms won't get you there. If you HAVE developed the vision, then you have no need for more forms. The tool (the forms) has fulfilled its purpose.
Recently, Sifu said something very interesting. He said that we train for two reasons: self defense, and health (fitness). The practice of kung fu is for these two things. He then said that if you don't want to learn the complete system, you could study for one year with him and learn plenty to be able to fight with, plenty to develop fitness and health, and you would not need to learn any of the forms. It would be a stripped down version of the system, just focused on the fundamentals. Because that is what is really important.
So yeah, I think you could do it, provided that you understand your fundamentals and basic techniques very well, that you are doing them correctly and don't need ongoing correction, and that you have a vision of what is possible and what you can do with what you have. Are you there already? I dunno. Might you need some amount of training to get you there? I dunno. You need to answer these questions for yourself.
But yeah, it's possible. You don't need to train under someone for years and years, and you don't need a belt of any color.