Everybody loves Tzeentch. If you don't, you will, or it was all part of the plan. Even Creed can't surprise this magnificent bastard. Or can he? Just as planned.
Now, the Changer of Ways may have some awesome scheme for everything, but I don't see how his Daemon army fits into it. Mono Tzeentch blows. All mono god lists blow (Slaanesh swallows) to be fair, GW designed the book to encourage mixed lists, but they didn't have to neuter mono god for the fluffer nutters out there who happen to like winning the odd game :P So now I'm going to slog through the pure Tzeentch build and see if we can make something unshitty. Yayz.
Tzeentch units, for the most part, are shooty. That's great and all, but most of it is short ranged and anti-infantry. To beat mech armies, you need bolt. Tzeentch armies, like any other shooty army, need to get their enemies out of their rides so they can't beat on them in HtH. Tzeentch sucks at HtH. Once they are out, you've got anti-infantry torrent fire on everything to blow them away. What Tzeentch does have going for it is duality. Every Tzeentch unit that isn't shit can do anti-infantry and anti-tank. Horrors are a necessary evil, but they can provide sufficient torrenty firepower and the odd Bolt to surprise people.
Blue Scribes (why not?)
3x Herald of Tzeentch - Chariot, Bolt, Breath, Master of Sorcery
3x Flamers - 4, 1w/ Bolt
Horrors - 8, 1 w/ Bolt, Changeling
3x Horrors - 7, 1w/ Bolt
3x Daemon Prince - Mark of Tzeentch, Bolt, Daemonic Gaze
Total - 1998
Tzeralds, Flamers, and DPs are all your primary tank busters and genera purpose awesome units. They can hit infantry or tanks with good results. Flamers and Tzeralds are your CC units, kinda. Jump Infantry/Jetbikes with uberflamers will reduce most units to ashes, especially if you concentrate your fire or just recently relived them of their transport. They can also spit out 15 Warpfire shots at BS4. DPs can CC, but they aren't the best at it (T5 4++ isn't very tough). The Blue Scribes are there because he might surprise you. You could easily drop him for another Tzerald if you can find 10 points, but it's not a huge difference.
Every unit is disposable, every unit is versatile (good againts infantry or tanks, up close or at range, sorta). This gives your opponent no obvious targets and embraces the MSU style fully.
Scaling is tricky without seriously reducing your overall firepower, but stick with the basic ideas and you should be ok.