Alembic83, I don't think that the strap is going to make a huge difference, it might help in the surrounding spot a bit, where it rest, but it's the law of physics in the end, if its heavy, its heavy... I got myself a nice comfort strap, I cannot use it anyway.
Regarding the weight, the 2 pickups vs 1 is not that easy to compare, because for a start one SB pickups weight 1/2 pound each! then My SB900 (2PUs) is heavier than the SB1000 (1 PU)...
My Arialembic (ex SB Elite 2) is so light... The older SBs were heavier in general, the newer ones where lighter, like the Elites and SB-Rs as you noticed, BUT, as you said, it much depends on the wood as well, definitely. Saying that, I read people saying that their SB-Rs were heavy, could be older one. For instance, the SB-R150 were very heavy, it used Zebra-wood.
The sad thing is that I much prefer the tone + feel and action of the heavier one
If I can rescue my SB900, I am going to make it an Arialembic LG MK2, and will probably sell the Arialembic MK1