I LOVE the idea for the plates. If/when I run out of room, & need to pack more, I'll be employing that method!
Unfortunately, I do not know anyone that reloads. I do, however know of an outdoors store near me, that has said re-loading supplies. Perhaps Monday I'll head there & see if I can acquire some of them lead BB's. I've got the copper BB gun type BB's but I don't think they are as dense as the lead ones are.
No more Tamiya gearbox's here! I still have 3 in the parts bin. I don't like how fast they break.

I've ordered a couple motors from the interwebs, as the servo idea
WON'T be an option on the Delta loader. Found these on Evilbay, & decided I'll try to fit them in it. SOMEWHERE?
https://www.ebay.com/itm/DC-3-6v-Gea...72.m2749.l2649
IDK if they will fit in it, or not, or how well. Once that
SLOW boat from China carrying them arrives me, I'll find out if they will work.