Any other airsoft guns are TM parts compatible?
JG makes a 416 that is TM compatible. Generaly speaking I would rank JG lower than ICS for quality but I don't care for the ICS split gearbox so for me it would be a tie or a slight edge to JG.
Any airsoft guns that has the ICS design?
There are basically three different types of splitting gearbox systems.
The ICS design which is only made by ICS and IMO the worst one.
The WE Katana which is new to the market. It has many TM compatible internals and has a removable cylinder design similar to, but not compatible with a PTW. The Katana IMO has a lot of potential but it's still relatively unproven. They do not make a 416.
WE "KATANA" M4 AEG - YouTube
The Systema PTW design is generally regarded as the Ferrari of airsoft guns. It's copied by several companies of varying quality, most of which will cost you anywhere from $1,000-$3,000. A&K and the DTW are less expensive clones ranging in at around $400? but have generally poor reviews. Most PTW's are M4's, the only 416 PTW's are made by the high end companies and run $2,500-$3,000.
**edit G&G is in the process of bringing their own split gearbox design to market.
Any parts I can mod to increase recoil?
No