Its far more complicated to do properly than you might think - on account of FPSC not having the capability to allow the user to precisely control all of the requirements and there are a lot of those to consider.
An invisible platform (Lift Platform) might do the trick - together with a visible object to make it look as if it was that which was actually moving the player.
The Jetpack is not really suitable due to the lack of those control features as mentioned. No combination of FPSC features or functions currently available are ideally suitable for lifting the player vertically in a straight line upwards - starting and stopping with precise control. All current ones have problems associated with them and do only a partially successful job.
You might as well use a teleporter or lift and be done with it. At least they work and are easy to impliment.
Anything else and you are asking for as lot of hard work and effort for less than ideal results.
From you picture - looks easy dont it? I can tell you its far from that.
A switch and lift platform could be used, platform, path and switch could be used. Currently available ladders could be used. Combinations and variations of all these could be used but the only ones that work correctly are the default lift and teleporters. Otherwise you are left with stairs.
FPSC has not been built to allow users the flexibility to do in this case what may seem like an easy thing to accomplish. You are given some default options for moving the player upwards namely, stairs, lifts and teleporters which are somewhat partly limited to use in single player games. Ladders proper are out by order of TGC. TGC has not to date thought it needed to include any further options or user additions - you use the default methods and thats all you are expected to require.
If you want more then the engine will give you no help - its partially designed that way. Its a click and play engine by default. You use what your given unless one is clever enough to find a method of overcoming its limitations and in most cases thats very hard and in some instances just impossible to do. You cant make it do what it cant do and it cant do what you are asking, simple though it may seem - its not in reality.
There may be someone who has done this and achieved perfection of control - I have not been able to find a way of doing what you want perfectly and all the options are a poor substitute for doing it right.
Using the available working deafult features you can do it - disguising them appropriately if need be, but you just cant overcome the issues that are attached to anything else as the engine does not provide support for it.
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