Have you considered to replace the Pokemon sprites and/or add mega-evolutions?
I had started work on modifying the G/S/C sprites for use in this hack, but I stopped that pretty early on. There are a few images I posted for them some pages back. I wouldn't consider porting sprites from later games into Throwback, as they use an altered art style and shading from the original games. I want to keep the game's roots in its classic form and add features from the later games that are appropriate and don't change the game's mechanics at large.
As for your other suggestion, read on.
Good Idea! I like the idea and good job done I'd say!
I have a suggestion that you should also make Hoenn and sinnoh pokemon Available to make it more Spicy!
Spicy, you say?
The point of this hack is to create the best, most faithful version of the 1st Gen games possible while not extending far out of the bounds of the initial remake (FR/LG). Adding Pokémon from later generations, especially those beyond Hoenn, would defeat the purpose of that. Where would I even put them, anyways? The main areas of the game need to strictly hold Kanto creatures, otherwise the experience won't feel as true to the original game. This doesn't leave a lot of room for the Johto Pokémon, which are all in the Sevii Isles. However, I can at least keep them because the base game makes use of them in the first place, and they still elicit similar nostalgic tones as the original 151.
The same can be said for new mechanics as can be said for new Pokémon. I never included the Physical/Special split because that radically changes how the game is played and makes different strategies necessary. I'd even partially say the same thing for abilities. I'd have implemented a way to make both of those things toggle-able if I knew how to do that (or if that is even possible). And mega-evolutions? I haven't been paying attention to the hacking scene since X/Y released, but have there even been any hacks that implemented that? It'd fit in the same category as the other examples.
That said, people are free to add these features into the game after using my patches if they please. I just have no plans to put them in unless I learn of a way to make them not mandatory.
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For those curious, I have put some work into another patch for the hack. As some of you may have noticed, in the GB music patch the noise instruments are only roughly approximated. Well, I've since found the data in the original Red ROM that holds what precise noises play for each of them and have fixed the sounds in the hack accordingly. Sans a couple of problem tracks, I'd say they're actually now the most accurate tracks in the songs they're in!
I also plan to take another look at modulation in the square and triangle tracks to make them even more accurate. Beyond that, who knows what I might do for this hack? :)