I've been playing this game quite a bit over the past few days, and I think it's a wonderful addendum to the original game. There's just a few things that I would personally like to see added into this game that I think would make it even better.
-More Sonic Medals
The whole goal of finding Sonic Medals to get a completed level on the map was really interesting, but I feel like there really weren't too many to collect, and almost all of them were up above springs (I can only recall 3 instances in the entire game where this isn't the case). If it's possible to add more to the levels, It'd be really nice to see more of them hidden in the nooks and crannies in each level (they could even be included in Gene Gadget/Panic Puppet for slightly more things to do for 100%). Since they're not used for Continues anymore, and getting to 5,000,000 points already takes quite a while to get to currently, I feel like this would add to the enjoyment a lot.
-More Points in general
There's quite a few things in this game that don't really score points like a normal Sonic game would, and I think it'd be nice to have a little score boost here and there aside from the minimal 100 per robot and 2000-something when passing the giant rings.
Things that could grant points could include things like:
-The bumpers in Spring Stadium (just like the bumpers in Spring Yard/Casino Night Zone)
-The rocks in Volcano Valley (just like in Hill Top Zone)
-Pillars in Rusty Ruins
-Ice Spikes in Diamond Dust
-And probably some more stuff I might be forgetting.
It may not be much, but it's nice to have little bonuses for such things like that, and again, it'd make the effort to get to 5,000,000 points just a little less rough.
-Different Time Bonuses
Sonic 3D Blast is a much different game from Sonic 3 and Knuckles, yet for some reason it's always had the same Time Bonuses as it, despite the fact that beating a level in under 60 seconds is impossible aside from select boss battles (only 4 of them I believe). It'd be good to see Time Bonuses more suited for this game, where levels are normally around 2-6 minutes long, perhaps with different Time Bonuses for Time Challenges and/or boss fights. Again, it'd also help even more with reaching 5,000,000 points, as well as make Time Bonuses feel more fair overall.
-Another Extra Mode
This one is just my opinion, but while I really love the Time Challenges, it'd be cool to see some sort of mode similar, but where you still had to destroy all the robots to progress. No flickies to fuss over, just destroying them all. The Time Challenges are very interesting but ultimately you can just forgo huge parts of levels just because they have no worth whatsoever, and I think an extra mode would solve that issue. Also, yet again, it would add another thing to be able to do while on the grind for 5,000,000 points.
These are my own little thoughts on this hack, but around everything else about the hack is perfect to me, and I can't wait to see the full version with the Time Challenge times fully worked in.