Consider taking an idea from Squadron strike: Different coloured risers. White ones mean 1 level, light blue ones mean 4 levels, dark blue ones mean 8 levels.
It means you can have many different levels without the miniatures wobbling on metre tall poles.
I hear you on the tall risers... I hope to find and stick with clear poly in 1" segments each representing 500'..that way 20"s for 10'000 should not be too bad. (maybe 1/2" if it's ungainly)
Man the guy J. D. Webster behind "Whispering Death" has gone above and beyond with his data and research. Obviously a labor of love.
I plan to buy his work and retro fit my vision into it. (3-dimensional combat, cloud layers.. Prevailing winds.. Likely maneuver templates Ala Xwing that include altitude)