As I see it, the Sandbag is a refreshing reason for me to actually play the stage.
Prior, it was just a longer FD with different blast zones. If I want to play an FD like stage, I will just play FD.
And who ever said that the WiFi waiting room had to be neutral? If anything I would put it under counterpick even with the Sandbag as a dollar like it was last build. The stage itself was so large that I would argue it effected gameplay too much to be a true neutral. It really just promoted hardcore camping and spamming with such a huge platform to play on.
That is just my opinion, but here is an even better point. Do we really need more neutrals? As it stands we have Final Destination, Battlefield, Yoshi's Story, Smashville, Pokemon Stadium 2, and Wario Ware as neutral stages (some may go against Wario Ware because it is so small, but with the extended blastzones I feel it is fine). That is plenty of neutral stages as far as I'm concerned, and that is only a conservative list (some use stages like Delphino as a neutral). I would MUCH rather have a more diverse set of stages to play on than more neutrals. I can't really say which I like better concerning Deadlands or the Mansion (I love the Mansion as a counterpick, but I did grow attached to Deadlands), but the Sandbag is a great addition. It makes for a more diverse counterpick list which makes for a more diverse game overall.
I would suggest to slow down the stage though, for the same reason as to why Luigi's Mansion was slowed down (the mansion returned too fast to actually allow players to take advantage of its absence). You should be able to get rid of the Sandbag and actually have time to play without him. It would force characters to actually put effort into keeping him onstage if they have no other way to deal with projectile spam, and actually reward the characters who would rather have him off the stage for doing so.
Personally, I applaud BBrawl for taking the initiative to create a more diverse stagelist (probably the only thing I think they did right to try to do). Some just flat out don't work, like Spirit Pillar and Temple, but others like Mushroomy Kingdom 1-1, Big Blue, and Green Greens (<3) become much more playable with the changes, and can really be considered for viable counterpicks. I can't wait for further possibilities because a viable Port Town would be amazing to add on to a hopefully growing list of counterpicks.
As far as hitlag is concerned, everybody give
this post a read if you haven't. Really shows how little the change actually does. I looked at it myself, and he is right; most attacks have like 1 frame of extra hitlag in 60% compared to 50%.