It can get better. I mean, this would be limited because this wouldn't support colour themes natively. You still wouldn't be able to assign such an RGB colour to "info text" echoes, for example, without compromising the ctrl+k+0-15 colour range.
This is the whole point of having a local colour range: to make it work with mIRC colour themes. Otherwise, of course, a simple RGB switch for /echo would be sufficient... but it's not.