Your characters are awesome just accept that now. Anything we consider difficult they should be able to solve given the tools and time However that does not mean everything is reasonably possible.you cant create a worm hole tooling around in your garage. This stuff takes billions of manhoirs and trillions in other resources assuming its physically possible at all. Your challenges should be somewhere in the middle. Crack the system in five minutes. Reroute and reignite the fusiongenerator. You're allowed to go a little crazy here. Just understand. These impossible tasks are now just difficult and in fact achievable.

You might be better thinking about this slightly differently. To use the specific example of building a robot: gGiven enough time and a reasonably high Hardware: Robotics skill there shouldn't be any difficulty at all for a player to physically assemble a robot and you might not want to have them make a roll. Where it gets tricky, time consuming, expensive and not guaranteed is getting all the bits and pieces together. - They need detailed schematics for the robot they're building. They may need to make a Hardware: Robotics check and take the time to design the plans themselves or use networking/rep and/or credits to license blueprints. - They need access to a large enough and high-quality enough maker to run off the parts. For a large, complex robot they will almost certainly need a suitably precision maker to accurately create parts, and will almost certainly incur expense for the uncommon ingredients and amount of material needed if the robot in question is more than a simple, small bot. - Depending on the hab they may need special licensing or permission to have the bot active depending on its functions. - They need a full OS, security software and the time to install, run, and customize all its settings to work with their controls, which could be many Interfacing, Hardware: Electronics, Hardware: Robotics, Programming and Infosec checks, all of which will take time and (likely) all of which aren't at the same high level with access to as many positive situational modifiers. - Specific skills for the bot will almost certainly require the purchase of skillsofts (unless the player has huge amounts of time and a high score in the relevant skill or access to brain maps of people that do), which can get pricey quickly. - Specific components - traits and upgrades - will all have their own time and cost to acquire. These considerations should meet your concern for being realistic, carefully considered and consistent across most of the setting. The player can decide how ambitious their project is and act accordingly - in a "minor time skip" that may mean they only go for making a few little camera drones on the cheap and at low or no difficulty rather than assuming one or two checks against maxed skills will net them a personal ninja death droid that's also a 5-star sous chef. This can be a good roleplaying process as well if the player comes up with interesting ideas on how to get these pieces in place, and using favors is a great way to build and reinforce relationships with ally npcs, etc. Big projects could also attract attention in their networks and hab, so if and how they go about it and what they're working on could also be story seeds.