Hello! Good questions.
1 - I have not thought about them taking a while to be built but it could be added down the line.
2 - The current Martian Machine designs are not final.
3 - Yeah.. that's a bug that I need to fix, It wasn't meant to force you back to the start.
4 - I haven't added the death to the Martians themselves yet.
5 - The dead Flying Machines can be found but the Handling Machines don't have a death yet and continue roaming [same with the Martians].