Nothing

You could always lateral to a bank (many are hiring, including FTP if you're diehard fintech) and jump to investing that way, but I think the switch is doable now given your interest in staying within your sector. 

Your advantage over bankers/consultants should be deep sector knowledge and the beginnings of a sector-specific network as well. Fintech broadly is a space that almost every growth fund looks at and if you can demonstrate true knowledge of 1-2 thesis areas, the drivers, relevant players with context from your strategy role I think that will be significantly better than the exposure you get making industry coverage pages as a junior banker. Many growth funds rely on junior to source, hence why having a real and demonstrated interest in tech is important.

How much exposure to you get now to the corp dev / venture team? I think lack of transaction exposure might be the only hindrance - you don't need to get in the weeds of execution, even consultant-esque tasks e.g. market mapping, helping rip through a data room, etc. will be helpful in telling your story.