Re-Apply to Entry Level IBD Positions a year after Graduation?

You won't be able to qualify for "Class of X" positions that are aimed at students who haven't graduated yet but there are plenty of experienced hire positions. Churn is so high - you will be surprised at how many there are. The caveat is that a lot of the time you likely will take a downgrade in seniority; re: anywhere between a half year and a full year not counted toward your seniority at the firm (1.5 years in consulting joining as a fresh year 2, etc). Also I think it is unlikely you chart anywhere without at least 8 months of experience on the job as well. Frankly I like your plan and this is very doable and in my opinion a much better route than doing an MBA as:

1) The opportunity cost of an MBA is massive

2) MBA with no IB experience only just navigates you to IB to begin with

3) If you ever want to go PE, would say ~90% of Associate positions are pre-MBA ONLY with post-MBA positions only going to Senior Associates / VP, and thus by doing an MBA with no IB experience prior you essentially gatekeep yourself from many attractive PE positions (won't ever say something is impossible, but note it is very difficult; I have friends who have had trouble re-recruiting)