You know if you're worried about certain smashes being too good on Ice due to sliding and hitboxes, you can simply change it so that the smash gives the character infinite friction having them stop on the dot like other smashes on Ice.
This would require work (obv), and naturally it's very likely to have undesirable side-effects elsewhere (like no momentum from dash cancel).
It would pretty much delay this set even more, and it comes down to whether or not people will support/play the stage to begin with. No point in making everything work out nicely for this stage alone only to have it collect dust.
And the stage does not a large effect on the outcome of a match up simply because you know how to maneuver the stage. I've played plenty of people on the older summit which has more ice on the base and ice on the platforms and they were able to adapt well enough to perform on the stage as well as they do on another stage in less than a few matches without knowing how to work the stage.
I don't think the issue of mobility and unfamiliarity is as much of an issue as what you're able to do with it
once you've gotten accustomed to it.
When you've learned the mechanics of the stage you can start abusing retreating DC Fsmash for MK/Sonic (more safe and more preemptive...yay?), abuse momentum from dash cancels (particularly good for those with short initial dash animations like Sheik).
Ice changes a lot of small little components that add up to be very different from how the game is normally played on the many other stages. Unique? Yeah. Give it a chance? Sure why not (for me)? But the biggest issue here is
will other people give the ****ed stage a chance?
It's a counterpick stage sure, but where do we draw the line at how skewed counterpicks can make match-ups be?
There's the issue of the stage's reception and impression, particularly upon newer players. This project makes itself to be rather serious and also expects people to take it seriously.
When people think of Brawl+'s goals, it's summed up (accurately or not) as "making Brawl better." What this entails is unclear I guess, but when someone plays this game in a side-tournament, and is counterpicked to this stage, it is going to bring the question of what this project's goals are (honestly or sarcastically responded as "making Brawl better") and probably also who is to say exactly what makes Brawl "better?"
I can see it now:
"Who are the clowns that thought it was okay not only to ADD this stage, but ALSO make it legal?!" People can be extremely serious about Smash Brothers (>_>) and even the most far-fetched or over-exaggerated criticisms can hurt our...image...(what was i suppose to type here).