While the numbers are all nice and good, there's one slight problem I see: dual stat synergy. Specifically, to compete, the sum of your Wisdom and the main stat must be equal or higher than that of the martial character's Strength stat.

To boot: you're assuming something reasonable in terms of potential stats, but while for another martial character only Strength is important, for a Monk using Empty Strike both Strength (or Dexterity) AND Wisdom is important, just to keep up. Now, that doesn't mean that will reduce the effectiveness of a multi-hit increased damage skirmisher, but it does make a dent on grapple because it's easier to skyrocket one score than both (inversely, and what I really see is the advantage, is that it makes you vulnerable to one stat).

So, let's assume that 20 STR is reduced to...say, 12 STR because of a Ray of Enfeeblement (a 1st level spell!). Net loss is 4 points to attack rolls, damage rolls and grapple/disarm/trip checks. You still have at least 5 points (or perhaps less than that, basically you start with a +1 over medium BAB and you get an increase every 4-5 levels). The loss will be a bit more important on disarm and trip, but you still can defend on sheer attack power and grapple.

Same thing on Monk, except this time is either Strength or Wisdom. You lose 8 points of either, and since the net loss would be the same on both sides, the Monk remains competitive. However, and this is a big one: if you get hit on both Dex and Wisdom, you get in trouble. You could argue it's the same for a Fighter that gets a negative level, but unfortunately it's an equal loss for both sides. So, if you get hurt on both sides, you end up losing more because you lose all those stats. Now, very few things affect Wisdom but there are lots of things that affect Dexterity, so you need to be careful about that one. However, while a martial character would only need to focus on two stats (Strength and Constitution, maybe Dexterity if you want to go with TWF), a Monk needs three stats to keep up (fortunately one of those is Dexterity, but you still need Wisdom and Constitution to keep up). What's more, you depend on two stats to be successful while a TWF character needs only one stat and the requisites for another.

But, that goes even further. TWF and Strength usually don't mix; TWF + Sneak Attack do mix, though. Or TWF + lots of extra damage (which is one of the ways you can play the Monk). But change the tactics completely, and you'll see a big difference; for example, how does a character that depends on two stats run against, say, a PA-using character, which only needs Strength to maximize it's capabilities? There are several ways to pretty much ignore AC, and one hit deals quite a bit of damage.

But damage isn't the thing; you've stated that the intention is "get a lot of hits while remaining mobile, and rely on two stats and increased fist damage to compensate". In that sense, it's not built badly; since you're applying a bit more static damage than dynamic damage on each hit, you basically compensate for whatever loss in attack bonus while undergoing TWF (same as how the huge damage gain by wielding a 2-handed weapon while using PA offsets the loss of attack bonus when using the feat). The thing is grappling, where every point counts. Tripping is special: you need a way to provoke attacks of opportunity so you might need a good Dex for that, which means either going Robilar's Gambit/Karmic Strike or using a reach weapon (such as the spiked chain), so it's quite expected that the Monk will be at least competitive until someone uses a guisarme or racks up the Tumble checks. Disarming is pretty much pointless, but the bonuses granted by weapons also count. Grapple, though, is the monster. You don't need to beat any other class on grappling; you need to beat the monsters on grappling, and that means compensating for being Large or larger, extra limbs and tactics such as improved grab. In that sense, every point counts, and those 5 points of non-existent BAB might be the difference between evading (or grappling) a monster and failing (on both accounts) to do so. Feats and abilities may make the Monk work it out, but the dependance on two ability scores might not be that good. And even then, the idea is not to make the Monk "just good"; the idea is to make it better. Consider that they get Improved Grapple, Improved Disarm and Improved Trip for free; unless that's something on my behalf, I think the devs had the idea that the monk would be as good, if not better, than the other martial characters at grappling, disarming or tripping (which, of course, doesn't happen; for what it's worth, they also suck on the other combat maneuvers, but YMMV on that one). Empty Strike, on that regard, introduces an artificial balance to the system which allows stacking two stats to compensate for the loss of BAB in order to use these abilities, which is my peeve; you have two chances to get hit on those scores and get your artificial benefit reduced to below effectiveness, causing you to turn slightly more dependent on boosts to ability scores in order to make that worthwhile.

Example: remember how by having 32,000 GP you can add a +4 to both Dex and Wisdom? Certainly that means you add at least two points on Dexterity and Wisdom when leveling up; a Strength-dependent character needs only to add his bonuses to Strength, so it basically balances up until you bypass Epic, but then again going epic to be better than the martial characters on those kinds of builds is kinda preposterous. In that regard, while still a bit artificial, the solution presented by the Pathfinder books makes slightly more sense; you're equalizing all factors, so that when everything is set and done, the Monk will have a better default score on those abilities than, say, the Fighter or the Warblade. That makes the Monk more attractive than a Fighter or Warblade in terms of making grapple builds (and with the increase in unarmed strike damage, perhaps doubly so), since the latter have increased feats and boosts that increase damage to compensate for the raw increase in dynamic damage from the increase to unarmed strikes.