I've been seriously considering looking into launching a CubeSat and it seems that the least of my worries would be design constraints. The money is less of an issue than the "why". There's plenty of information about how to build a stable cube-sat, but what actually can be ascertained about Earth without substantial investment? Is there something that lists all existing CubeSat experiments that can categorize experiments conducted, to avoid potential rework? What could my small team of 3 accomplish beyond the things NASA does with millions of dollars?
It might be good to then reflect further on why you have "...been seriously considering looking into launching a CubeSat..." to begin with. Perhaps it is "not because they are easy, but because they are hard; because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept..."
While "ascertaining things about Earth" is one function that a cubesat could serve (or the near-space environment), ascertaining things about technology and about teamwork are also valuable things that a cubesat project can yield as well. Some people explore the use of phones or Arduinos or Raspberry Pis or GoPros as part of their project for example, or to include transceivers that communicate with other satellites such as OrbComm or Iridium.
Those links are just randomly chosen examples from this site, there is plenty more to read here within Space SE and the rest of the internet about "edge-like" systems and ideas and applications.
The unifying thing among many interesting and valuable cubesat projects is that people just "try stuff" that hasn't been done before, or hasn't been done in a particular way.
While spacecraft projects that are sufficiently funded to choose their own launch can choose their own altitude and inclination, cubesat orbits are often deployed at fairly low altitude. It means that they can often be relatively short lived (low mass to surface area and so more "draggy", especially with pop-out solar panels) and don't necessary provide a good "sampling plan" for the Earth's surface. This is one reason why they are often "demonstrator" missions rather than full fledged science missions.
Choose something that really captivates your interest, that will allow you to keep motivated for years, and keep interested through all the tedium of applying for all required permissions for launch and for communications.