Why not open a SelfWealth account and have a go with a smaller amount? You could see how you go without risking very much money. Say you did it with 100 shares how much of a share price rise would you need to cover $19 brokers fees (a Buy and a Sell)? 19 cents per share? On Friday there was about a 60 cent range. Easy peasy
Actually, my brokerage is $6 or 6 basis points max. Even so, I'm not confident, because ...
... it's a very seductive idea to buy when it's a bargain and to wait till it's gone up a bit. I know that you haven't back-tested it over past data, but I have, FWIW. Like I said before, it's not impossible to make it work, but it's surprisingly difficult to outperform buy-and-hold with the banks (I know, it's not an ETF).
Anyway, it would not be particularly helpful to list what could go wrong. You might dismiss it, consider it unlikely or maybe able to live with it. Remember, I didn't predict dire consequences, only that your efforts would underperform the index in the long term.