Seems you got all figured out, great. I tend to do it too, but meta changes and new toons are added so things may differ in few weeks. But your reasoning is good and sound, no complaints there.
I put in a rough eastimate, based on previous tournament. I get 1k points from first day. And look how many points is top10 and top50. If its between 3-4k then it's easy to get in 40min, just a matter of ally points. After that I look how many toons and ally points I'm left with. If enough I push, if not I keep spot.
I usualy start with lowest units first. At start of tournament - all opponents give out similar reward. SO its easy to snipe even 40lvl units (had quite a few 30-40lvl teams this tournament). I save my strongest units for last - just because when you advance you get tougher opponents with best synerfy. So if you want to get fight done fast and rank up, better to go with best units. There's no sense to expect that top tier players have crappy defence. Overall - I try to snipe easiest units whenever I can, they sometimes give out 6/13 points instead of 7/14 but if I can save up a turn of my strongest units then its worth it ( as long as it costs less than 1k per unit).
So why would you invest in the future at a stage with low income? Rather aim for what you need now, and the event's rewards (other then the obivious shards) can be quite good.
It's a matter of efficiency. After 80lvl, you can have awful luck and get mega whales in your bracket or meet ppl playing for months with a vast number of units. They will easily outscore you. So pushing hard at that point is kinda pointless. It can be fun and rewarding, but more than often not. And at that point you yourself have quite a few units unlocked and are probably increasing your pool of units. With that being said, even those more rare units can have a purpose then - ewok squads for raids, jawa squads for droid event or mod challenges. Or let's say Cad Bane as scoundrel for heist. At that point you probably dont have such a high need to farm a toon or can spare energy to farm smth if you need it. Going for bronzium might reward you smth and push you to start farming it. And as a bonus, if you get shards of what you have 7* now thn you can just convert them in shard shop for smth useful.