Well, I for one would be very interested to see this game get expanded upon. I ended up playing this one the most out of lineup. If I had to narrow down why I suppose it would be down to a mix between my love for playing the odds with high stakes, and importantly following along with what happens to the horsegirls, former gamblers especially.
With that in mind, my feedback is that I would like to see both aspects of that part of the game expanded. On the more gamba side, I'd like to have more info on the girls available. Maybe not for free, but at least be able to get a way to see the basic stats of the active racers. Maybe even a way to change them, through sponsorships or shenanigans.
The second side is I would like to see more variation for the racers themselves. It would be cool if they had more that made the different than just color and invisible stats. Maybe their personality could make them more likely to trigger certain events, or different outfits and "equipment". Visible stats might also help with differentiation.
Side note to all that, It would be nice if there was a way to see who all is in the stables. It can get a little confusing keeping track of who is in and who got traded away. Might also be a good place to put some fluff, like who the trainer of the girl is. Could also lead into some fun events where certain lady trainers can get into some trouble.
Might also be nice to expand the gambler side of things as well. Considering the gamblers eventual fate, Maybe there could be ways to spend the money in ways that well help or hinder her in the future. Say, you spend money to rig an race but get caught, ending up with a permanent ball on chain when you eventually end up on the track. Maybe events that affect the player could occasionally show up, like a loan shark offering a tempting offer.
Sorry for the ramble, don't feel any pressure to implement any of the things I suggest. I'm just spitballing about what I liked and would want to see more of. All these paragraphs to say, I think the core of the game is very solid and it would make a good base to expand off of.