Here's what I do.
On a 5 or 6 weight, which are the rods I'm likely to be switching from dries to streamers on, I'll cut the tapered leader off at its 1x diameter. I'll then tie a tippet ring on. A piece of 3x followed by 4.5x turns it into a dry fly leader. For small dries, I'll add 6x to the 4.5x. When it is streamer time, I'll tie either 1x or 3x to the tippet ring.
On a 3 or 4 weight, I'll cut the leader at 3x and tie my tippet ring there. I'll then use it the same way as above but since only smaller streamers will be used on these weights, I'll never need to go heavier than 3x.
I only carry mono in two sizes and flouro in three sizes. This handles all of my leader altering needs. Well, there is a spool of 7x mono in my backpack just in case.