I would love to see a few different algorithms for the way portamento behaves, for example, an exponential curve where the rate of glide changes as it gets closer to the destination note, or a setting where each voice glides at a slightly different rate or with a slightly different curve shape. I've always felt that the linear glide setting in most digital synths is a bit lack-luster, especially with very big sounds with a lot of voices. Some variation in how the voices behave while gliding would create some powerful portamento options.
