I have experimented a lot with flyers, sappers and had a lot of success with them when I was active.
Having flyers combined with some game sense, means that you are basically using map hack.
I like to get 1-3 flyers, where I micro one of them and put it on a hotkey, and the others would watch key areas. With flyers you can basically always perfectly determine what fights you need to take and you will never ever be caught unlusted. Furthermore they protect against dks, and occasionally you can even use them to find exps. I use flyers vs. aggresive players.
As for sappers, they are amazing vs defensive players. If someone likes to turtle on 2-3 bases until he gets big, you can decimate him by being faster and finding key wall-ins, unit positons with 1 flyer. Sapps are best for breaking s9, 3, the back of 5 (1 sapp is enough for a sneak from the back attack when 5 is walled-in) and sapps are also great against distant exps, like 9/11 when enemy exps there from 2/12 or 6.
Fast flyers also allow you to hunt early dks, and scout enemy strategy.
Now, building an alchemist and getting a flyer early is costly, however with a cat and sometimes a tower you can live at 4/5/2/12/9/11 no matter how good someone is at aggression, given that you went at least close to even during early game. I have not yet found the perfect time to trainsition to alchemist units. I believe it is good to get them on 1 base vs 1 base players and on 2 base vs expansive players and play defensively until flyers allow you to have an unbreakable defense. When you are against aggressive players going 3/4 rax on 1 base, sapps can help you live, win engagements as they can take out 1-4 ogres. They are very hard to micro tho!
Another tactic I like to use is to have a sapp and 2 dks with haste dnd between 11 and 12 where usually people wall with a farm or temple. You can pre-haste the dks, sapp the wall and take out every peon at 11. It is just impossible to pull peons or to bring ogres in time. This works when enemy starts 9 or s9. It can be difficult to execute, as you have to be certain that the area under 12 is clear and late game this is a major hassle, but doable.
Against slower players, sapps and ogres can also overrun the enemy on 2-3 bases. I tried having double alchemists and pumping 2 sapps silmultainously to take out usually 2 enemy raxs at the same time. Rebuilding raxs takes time and losing them will throw the enemy off especially when you follow-up with more ogre pumping. You might lose the first couple of fights, but with your rax advantage and pressure you can still push hard enough.
Sapps can also work with ogre rushes. With absolutely perfect res managment this is a dangerous combo to occasionally use I believe.
I went through much more scenarios than this and had many more ideas that I could not try as I've had not enough time to practice.
Any thoughts on how good this is, or how to make it better, when to trainsition or how it felt to play against it?
I know that Braviet mimic'd this and also saw Viruz using flyers after our games.
Games vs Braviet would become boring tho as essentially there were 2 hackers sitting on their bases with 30 ogres neither attacking into defensive positions. Although hasted dks > Braviet runes. ;p
I won so many games with alchemist units vs so many players. Everyone essentially, so it should be an option to consider exploring! Really wish I had the time to perfectly implement my ideas but life is too good now!
Good luck haver fun guys~
