You can emulate waveshapers with steeper aliasing falloff than 6dB/octave, using integration-based techniques to calculate the average output value of a waveshaper when interpolating multiple input points (or something like that). There's a paper describing various orders at http://dafx16.vutbr.cz/dafxpapers/20-DAFx-16_paper_41-PN.pdf (if I remember the right link, RIP it's not HTTPS).