Since it's not interesting to reinvent wheel, it worth to inspect existing projects, and decide what can be done better. Here I will comment the most interesting ones.
28BYJ-48 based dispensers
- Solder paste dispenser by Geir Andersen.
- Arduino Motorized SMT Solder Paste Dispenser by Zapta.
- Solder Paste dispenser by Anuradha Gunawardana.
All projects above are opensource. But while those are very cheap and easy to do, BYJ motors are not convenient for compact design. If you have TS-80 or TS-100, you should understand what i mean.
- Electronic Solder Paste Dispenser V5 by Mike Menci.
Though that project is not opensource, it's very nice. Author is professional engineer and shares interesting technical details.
- It uses machined parts for pusher. May be nice for manufacturing, but not convenient for hobby DIY.
Let's try to formalize, what would be interesting to do (and why that combination of features will be new or unique).
- We need "popular project" - easy to do, no machining, cheap enough.
- It should be small, pen-like. Instead of syringes replace, it would be more convenient to have multiple dispensers.
- It would be interesting to support fixed portions dispense, instead of constant flow. But that requires additional considerations about interface usability.
Seems ok. Now we need to do some estimates about precision.