Great topic, @bgmoon!
Here are some ideas off the top of my head:
To pre-soak seeds, you could load seeds into a seed tray or bin and then use the watering nozzle to spray a small amount of water onto the tray/bin. Then wait a few hours before using the seed injector to pick up the seeds. Warning: sucking up water into the seed injector will cause problems with the vacuum pump, so you would need to make sure there isn’t excess water when picking up the seeds. To ensure you avoid that, you could 3D print a special “seed soaking tray/bin” that has a small drainage hole in the bottom, or just drill into one of the ones we included. To achieve a thorough soaking with a drainage hole you might need to use the watering nozzle to spray the seeds lightly every 10 minutes over 2 hours or something, rather than spraying just once. A problem I foresee is putting too much water in the tray/bin at once and seeds floating/getting knocked out if the container got flooded. You’ll need to do some experimenting (and share what you find! 
)
The only way right now to ensure you are not holding multiple seeds is to have only a single seed in the container when the pickup happens. The seed tray has 16 containers so that you can tightly control quantities if you need to, without having to reload after every single pickup. A way to partially control quantities from many seeds in a bin is by selecting the right needle. Go with the smallest needle that works so that there is as little extra air being sucked in that could inadvertently suction hold additional seeds. Thinking more advanced, there may be a sensor that could be developed for counting seeds, or a better needle design, or some way to dispense seeds into a pickup area in controlled quantities. Someone recently mentioned to me in an email that an airsoft gun magazine or hopper style mechanism could work depending on the seed shape. The challenge is most likely coming up with a system that works for lots of different seeds rather than a lot of hardware that only works with one type of seed.
All of our testing has been done outside in fair conditions. So, not still-air like in a greenhouse, but not high winds. I’ve only had seeds fall off when I knocked em off with my finger on accident. Further testing will need to be done to see how things work in higher winds, and what types of measures are needed - if any - to prevent seeds from being blown around.
Nothing about the vacuum needles in the current design facilitate seed orientation. Perhaps a special 3D printed “staging area” could be made where the seed injector drops a seed on this staging area, and the topography (top surface) of this area facilitated orienting the seed correctly. Then the seed injector could pick it back up for planting. Just an idea. I’m not too familiar with this and it seems like a tough challenge given different seed shapes and how small everything is!
For covering the seeds with loose dirt, you could probably use the weeding tool to push up to 1cm of soil around without it popping off the UTM (depends on how soft/loose your soil is of course). Maybe you could make another tool that is just for this purpose? Just a plastic piece with the magnets and a flat area (similar to the weeder blade) that could be used to do very minor earthworks?
I’m pretty excited to see where this topic goes as there are potentially hundreds of ways to dispense, count, orient, soak, pre-process, and plant seeds!
)