I think you should just give it a go. There’s probably not much benefit in getting any more qualifications, particularly if you’ve already got [[ACA]] and [[CTA]] already.
Just one thing though. If you do go to an investment bank, it probably makes the most sense to not end up doing a finance or tax related role, otherwise you’ll just be doing mundane finance related work.
There’s no harm or real risk in what you’re doing. ACA CTA will always be massively in demand and well paid- you’ll never have a problem getting a job or putting food on the table. You’re in a fortunate position to try going after your dream job and seeing what happens, with little chance of fallout!
Remember though, if you are looking at getting into investment banking, don’t expect any bonuses (or even much luck getting in) until after the market improves. Which could be some time yet.