>a lot more appearances from May, who's slightly tougher to beat
She wants to beat you when it comes to filling the dex first, so she should appear throughout the region looking for Pogeymanz, and be slightly tougher to battle, with the reason being that while you're healing up at the Pokemon Center after your loss to her, she's gaining ground when it comes finding 'mon and filling the dex.
>slightly more appearances from Wally, who's a lot tougher to beat
Unlike May who wants to beat you at filling the dex, Wally just wants to beat you in battle. He needs to appear more so we can really see him go from a weak, sick kid, to the bad-ass who made it to the end of Victory Road before you.
>slightly more prominent role for Vito
His family talked so highly of him, and then you finally meet him in Victory Road and he's meh-tier. Doesn't even have his Alakazam. I think it'd be cool if he made a few more appearances as a pseudo third rival.
>Frontier from Emerald
>online Contests
>Challenge Mode
>the 10 or so Cut-able trees throughout the region to just not be there in the first place
>acquisition of the Exp. Share remains the same as it was in 3rd Gen
>more Trick Master
>after you finish all of Trick Master's puzzles, before he goes to distant lands to find new tricks, he tells you to look after his house, allowing you to build your own puzzles, and your friends can play through them over Wi-Fi
This would just be fucking rad.
That's about it.