So, to summarize a bit.
With €780 for the Platinum and for the first year only, we can get:

• a 3:1 MR points ratio (earned) with the booster offered
• a 50.000 bonus points offer, that can be converted with a 2:1 ratio into M&M miles, totalling 25.000 award miles (is that correct?)
• at any moment you can swap your MR points into M&M miles with a 2:1 ratio
• a second Amex Platinum card for free for your partner, if needed
• 4 Amex Green cards for free, if needed
• fast lane at BRU for 2 people
• PriorityPass lounges included for 2 people + 1 guest (each) = total 4 people
• discounts and upgrades at Avis and Hertz up to 15%
• you can keep getting award miles with M&M without interruption (by converting MR points into miles)
• some other Amex perks (300€/year discount on select restaurants, loyalty programs with some hotel chains, travel insurances, locksmith, etc.)

Am I missing something? Is the above correct?
Even just considering the first 7 points I find it quite interesting. It's not a cheap price, but I personally would have no problem in just testing out the first year of this offer, while we will see what comes out of BeoBank after a few months.
And even if you don't want to pay penalties with Amex with early termination of the contract (if any), you could just wait the entire year and then just refuse to renew the following year. At that point, the "retention offers" on Amex side could also be useful.

In the past I have used the italian M&M Mastercard Gold for many years, and acceptance was better than Amex as usual. Earning was 1 mile for 1 € (don't know current rates).
But I have to say, at least in Belgium since 2020 when I got the Amex Brussels Airlines, the situation has improved.

What do you guys think? I admit I like the idea of dropping Amex, but that would mean not earning award miles from November to July (or whenever Beobank is ready) – and their current offer is quite good, all in all, in my opinion.