I really want to see us transition Parker out of the midfield. He's a very good forward and I think it's time to put the much more dynamic Heeney there and let Parker be 90% of the forward Heeney is anyway. Mills is 10+ weeks away and has his own issues. He didn't play much midfield at all last year. Adams shouldn't be a problem but we're talking Horse so he could be.
Ultimately, I think Heeney is just a low risk pick. He was injured last year and so his scoring dropped off ~10 points from his normal scoring when playing as a forward. If he just gets back to that, he's a good pick and a top 5 forward barring significant changes. This role is just icing on the cake of an already sound pick, if he keeps it and plays even close to tonight, he's a legit F1 candidate as you said.