Bit late at night for properly explaining why this would be worthwhile, and probably not set to be a popular concern, but nonetheless:
The gain knob on tracks enables the addition of up to +18dB of gain. But the clip gain envelope only allow up to +6dB. Would be nice to have the same range available to the envelope.
I'll try to explain why this is:
Often, particularly on vocals, I prefer to automate the gain, rather than the volume. This is because the gain happens at the start of the chain, and thus affects how the audio hits effects, particularly compressors, downstream. Often, the best place to do this is with clip gain envelopes. And it's easy to end up in a situation where you've already done a lot of clip gain edits, but get to a point in the track you're working on where you need more than +6dB to work with.
Of course, you could go back and reset the baseline you're working from on the compressor, but you'd have to re-work all your prior fine-tuning. It seems odd to me that clip gain envelopes don't offer the same range as the knobs.