The biggest problem is that your cash cows aren't really worth enough yet (apart from Hall) and like everyone else you are starting to run out of trades.
I think you need to get Swan in your midfield somehow. Personally i'd swap Martin and Zorko, and upgrade Martin to Swan. You have enough cash... Only downgrade Hall or Delaney if you need to fund another upgrade. This is just my opinion though and it may be a little crazy- I currently think Zorko is a top 7 forward but this could change given his lack of AFL experience. It's just a risk that I took. Still, I think he will average more than Martin this year
Here was my other option:
Upgrade Delaney to Suckling, rounding out my defence.
Sub Chapman into the midfield for Zorko.
Downgrade Hall in the forward line for some cheap rookie that won't play.
I'm left with 3 trades and $346,000. I'm then banking on Marley Williams or Sexton to go up from 175k, hopefully allowing me to bring in either Swan or Ablett next week.
Risky going into the years with only 2 trades, but, what can you do!? I'll give your way a go, but I just can't risk wasting trades on Martin to Swan when I have so many rookies left...