I've decided to ask these questions here since I've probably wasted 100,000 miles in the last few years from bad decisions.

My primary motivation for collecting frequent flyers is to be able to get upgrades for existing tickets to business class.

About a week ago we flew (family of 3) air canada from sydney to vanccouver (also a qantas leg from brisbane to sydney)
somehow we got a free upgrade to business class, they didn't even tell us. not sure how that happens.
I didn't realise I had to sign up for aeroplan before that flight to claim those miles so that sucks.

but now I'm wondering are there any star alliance member that would let you retroactively claim miles if i wasn't already signed up, and combine the points form 3 accounts into one? or even better, somehow convert those combined points form 3 people into aeroplan miles?

I have another 10,000 miles on Aegean, but I'm considering ditching them because aegean doesn't let you give points to other people, and the lifetime gold membership is over. I believe aeroplan would allow me to collect the points from my families names into one or two accounts, because you can trade them, is that true?

I usually fly air canada and qantas, and recently i've been flying around 30-50,000 points per year.

I'm also looking at getting a new credit card to collect frequent flyer miles to be used with air canada here. I use an HSBC card in Australia for qantas, but yet to pick one for canada/north america. I am ok with paying a fee, and I balance my card immediately (I don't do debt) I would estimate that I could spend at least 30,000-50,000 on that card in the next year and put all my purchases on it.

I'm considering one from BMO that apparently can be converted into any kind of miles/aeroplan/quantas frequent flyer points you want, the BMO World Elit Card

I also wonder if a card would work well in USD as well as CAD.

Thanks for any tips, I'm sure any info will save me from wasting as many miles as I already have in all these different accounts.