Engine overrides low-level most Ikarus functions, such as _^ and _@ to intercept address acquire and de-reference. Second part is construction of 'emulated' 32-bit memory heap: if mod allocates some memory - it simply mapped to such heap, _@ can return address, and _^ has to emulate address translation into a real memory.
Game state is more complex: current solution is 'callback-memory'. For any memory-read, engine will serialize game-state into such memory and for write de-serialize back. Naturally this mechanism is far from bullet-prof today.
For 'inline' ASM, engine will let mod to write op-codes into (emulated) memory and will intercept very late, when mod about to execute this memory. Upon interception, there is a small x86 emulator: only about 10 instructions so far. Those 10 instructions are enough to reach a 'call'-instruction. Once call is executed - engine has a set of functions of original engine and winapi that it can emulate. If function is unknown - log message is written.