In general, I see that as being an archaic behavior that only serves to add fake difficulty, which is why it's removed - because the bomber is a useful skill for players and designers alike, but the timing it adds no real value. However, if there's ever a pressing need, I have built into the source code a compile-time switch which can restore the classic bombers (so for example, if I was building a custom-made player for someone who really really wanted timed bombers in their pack).
It's also worth noting that regardless, the functionality is still there - the change simply works by setting the countdown to 0 instead of 5. But even in a player that uses the instant ones, certain conditions can still give rise to a timed bomber - specifically, the nuke (which still starts a countdown from 5), and the radiation object (a NeoLemmix-exclusive object which turns any lemming that passes it into a timed bomber, starting from 9).*
I had considered even allowing it to be set on a per-level basis, but decided against it for similar reasons to why I hardcoded the "Sixes Not!" special effect instead of setting it in the level file (I actually did even write code to store that effect in the level file, but later decided to remove it - or rather disable it; all the code's still there except the line to actually read the value from the file has been commented out) - although of course, the traditional version would need that to be hardcoded *anyway*. xD
* I should add, so I don't seem hypocrital: My logic on this being okay is that the burden with the timing in this case ends up falling more so on the level designer than the player - there's no guesswork as to where to start the bomber, only a matter of where (and how) to get him for his detonation 9 seconds later.
