Edit: Disregard what you see here, I should read more before commenting
You can get around 500 SG just from collecting red boxes, it could take you around what? 2 hours to collect all of those? Probably even less if you were to plan an optimized route.
If you compare: What you can get creating another account and gifting the SG to your main in just a few hours vs. What you can normally get playing PSO2 in one week, the difference is massive.
Why would I play old PSO2 if this other option is way more rewarding, can be done faster, and I don't have to wait 7 day?
Why pay $20 (2000 AC since we can't buy SG directly anymore) when this other option gives me about the same amount of SG and is totally free?
Of course the common/casual players won't do this because it takes much more effort to set up, but the more dedicated players and whales would totally abuse this system if it ever were to be implemented, just like how they already do it to get quick meseta from the boxes.
IMO the better solution would be to make the SG items themselves be tradeable or giftable. Hell, let's go one step beyond, make all SG items sellable in the Player Shop, maybe at an increased minimum price compared to AC items, but at least everyone would have a chance to get them when the scratches are discontinued.