Axles spanning large gaps tend to bend and torque easily; VEX has clearly responded to the issue with the release of the thicker high-strength axles. I would like to put forth an idea to allow the thinner axles to be reinforced as well; a standard spacer contributes nothing other than, obviously, spacing out components on an axle. However, a metal spacer with a square hole instead of a circular hole could be very useful - the rigid metal and the restrictive square hole would prevent axles from bending or torquing. Ideally it should be less wide than current spacers are - it should have the same diameter as collars do. The reason for this is that spacers tend to be just a little too wide to fit next to gears well; they tend to rub a little, while the slightly smaller collars do not. It should probably be sold in 0.25" 0.5", 1", 1.5", 2", and 3" lengths, with grooves at 0.25" increments to allow for easy cutting to more specific lengths. Basically, the goal of the product is to have a metal rod that can be slipped over regular thinner axles to support them with significantly more cross-sectional area, so they don’t torque or bend.
I will try to make CAD models as well. 