angelfromanotherpin at [unixtime wrote:1204661434[/unixtime]]Why? It's a chase scene mini-game, not the climax of a race movie. I think that variety in chase scenes comes from the participants and the environment. I mean, if you're being chased by a man on a Dire Bat, he's not going to be impressed at all by how big a gap you can jump over; but if you go into the sewer, the guy has to get off his bat to follow you; and if there are no sewers, you might have to release the stock of a bird-seller to distract the bat; and if there's no bird-seller, well, you'll have to think of something else. I don't think the mini-game needs any more depth than that.
And this mini-game is going to have specialized rules for how bird-sellers interact with dire bats? And the DM is expected to decide whether there's a bird seller on this particular street, and that seemingly-arbitrary decision is going to dramatically swing the odds of the chase? What you described doesn't sound like a mini-game, it sounds like magical tea-party and DM fiat.
A much more plausible-sounding scenario would be if you make a wisdom gambit to find "something" that can distract/upset "a mount," and if you succeed, the DM narrates it as releasing a bird-seller's stock to distract the dire bat. That's a level of abstraction where you could actually write general rules, and expect people to learn and use them, and establish some kind of balance.
But either you're doing "a generic [stat] gambit"--in which case every chase is going to be pretty much the same, apart from the narration--or you're using your special "distract enemy mount" gambit that only works against mounted pursuers, targets your pursuer's ride skill, and gives him the choice of either soaking the distance loss and making a save to avoid the "recalcitrant mount" status or abandoning his mount to continue the chase...which is precisely the sort of thing I'm talking about.
But that gambit
still isn't dependent on the dire bat and the bird-seller, specifically, because that's way more special cases than a sane rules set can handle; you'd use the same ability (maybe with a different modifier) to scare off horses by setting something on fire or confuse a shark by releasing a screen of bubbles, if those were circumstantially appropriate.
And I would probably separately quantify the prey's lead and the pursuer's knowledge of the prey's location (so you can tactically differentiate cover/tracking from distance, and the guy on the dire bat can choose to try to follow you above-ground when you duck into the sewers, risking losing you to avoid the mount/distance loss). Being farther away generally makes you harder to track, and concealing your position makes you harder to follow.
angelfromanotherpin at [unixtime wrote:1204661434[/unixtime]]And what do these obstacles effectively do besides lengthen or shorten the lead?
Incentivise or disincentivise various actions the pursuer can take.
For example, maybe the pursuer always has the option of running straight after the target or trying to find a shortcut to cut him off (more risky, and possibly sacrifices some knowledge of the target's location/route). If the prey tips over a fruit stand as he runs by, that makes running after him harder, which will ultimately result in a distance increase if the pursuer continues straight after him--but the pursuer has the option to ignore this penalty if he decides to try the shortcut strategy.
This way, the mini-game involves trade-offs, evaluating the circumstances, guessing your opponents' stats and decisions, and other such tactical considerations instead of just rolling your highest stat three times.