Dex tank - what can be done?

[Heavenblade]

Probably not huge news for everyone, but swordsages can be pretty good battlefield control tanks with a pure focus on dex.

Taking spiked chain, finesse and shadowblade, combat reflexes is based on dex, add on stand still and you are prettyy much good to go.

Mithrral medium armor+dex+wis is pretty high ac, which is a nice boon.

Since you can influence a lot out of turn, it makes full-round maneuver recovery less painful, and strikes etc. mean you can utilize move actions for ssmart tactical repositioning.

If you manage to get dex to damage in another way, snagging thicket of blades through martial stance is also neat.

Question is - what else can be done to make this mobile dexterous battlefield controller more awesome?

[Aegis013]

You can always look at increasing reach (e.g. Willing Deformity + Willing Deformity (Tall) feats and/or Aberrant Blood + Inhuman Reach) or size. This gives you a wider range of battlefield control/influence. A reach weapon is also a go-to for improving on this front. Guisarme or Spiked Chain are usual suspects.

You might consider a dip into Crusader to get Thicket of Blades, although you'll lose some damage / save DC on standstill if you're not in a Shadow Hand stance (could have both using Master of Nine, but the feat taxes for it are miserable).

You can save a feat with a two level dip into Wolf Totem Barbarian which gets Improved Trip without the pesky pre-req.

This one is a little worse overall, but three levels in the rather lousy Knight class gets you Bulwark of Defense, which makes your potentially enormous threatened area count as Difficult Terrain for anyone who starts their turn in your threatened area.

[ExLibrisMortis]

The biggest problem with Dexterity-based lockdown is the lack of synergy with Trip and size increases. Damage is good for interrupting, but Trip (or Knockback, grapple, etc.) adds something extra. So you'd like to add some other rider effect to your attacks, and it has to be something that works on a single AoO and doesn't depend on Strength (e.g. not Three Mountains Style). Dazing Blow (the war troll ability) would work, and you can get it with (draconic) polymorph, but if you're taking the form of a Large troll, you might as well use its Strength score to your advantage, slightly undermining the Dex-based concept. Still, worth a look. I'm sure there are other cool rider effects (Death Devotion, psionic minor creation for black lotus poison, etc.) that suit Dex focus a bit better.

Decisive Strike is a good addition to anything based on AoO usage. Combines well with counters and boosts, not so well with strikes.

[Anthrowhale]

Per ExLMs point, some possible choices are:
Devoted Inquisitor (Smite+Sneak -> save or daze)
Head Shot (Sneak 5d6 -> Save or Confused)
Maiming strike + Double Hit (1 Cha damage/2d6 sneak => 10 Cha damage at high levels with 0 cha = vegetable)
Staggering Strike (Sneak -> Save or Staggered)