My best idea for multiple hud xhairs would be to use close captions. Make a font similar to fog's crosshairs and the cc file to have a, b, c,etc and then use the cc_emit (with an extended linger time) command to bring one of them up. I gave it a quick attempt but gave up, it'd probably have a lot of alignment issues but I still think it is possible if someone with more patience attempted it.
Other xhair methods would be playerclass (vtf only), achievement tracker, netgraph and loading a vtf through tf2 (using size to toggle off). You could also have an xhair for your stickies only by editing the hud charge assets.