Would it be possible to register a team and submit it into competitions during the middle of the season such as now?
Depends on a couple of factors. Has your team already built a robot, even if it’s one of the standard Vex bots like Lift or Claw? Are there tournaments remaining with open spots in your state/region when you check Robotevents.com (even if they show 0 spots open you may contact the event organizer and see if they can add your team)?
I assume your team is already formed, and have a practice field. While it is later in the season, you can still register and attend tournaments to get the experience for next season. Even if your team decides not to register, I would suggest you go to a tournament or two and watch from the stands, check out some teams in the pits, maybe talk to them to get ideas, etc. for next season… and build a robot anyways to practice and get ahead for next season.