Using the latest version of Unreal Engine, implementing a slice mechanic and building a proof of concept game using these mechanics could be done in approximately one week, a breakdown of how time spent would be as follows;
Day 1: Quick concept art, discuss ideas for mechanics and gameplay, as well as other things like target hardware and audiences
[Milestone 1 Paid]
Day 2: Start testing in Unreal, see how the slice/dismemberment mechanics can be applied to various objects (Humanoids or environment and prop elements)
[Milestone 2 Paid]
Day 3: Build out game around mechanics with placeholders
Day 4: Continue building out game, start on UI and UX, sound
[Milestone 3 Paid]
Day 5: Implement polished assets & test for balance, bugs, performance
Day 6: Send executable for testing, playtesting
Day 7: Fix any outstanding issues and tune anything that didnt feel/work right, deliver finished project files.
[Milestone 4 Paid]
If you have any questions on the project or previous work of mine, feel free to contact me at any time.
Thank you and have an excellent day.