I know other people have probably made a suggestion about adding more suits but mine is a bit different and I'll explain why. Career mode is probably going to be added within the next update or two so I think this could actually fit really well in that update. Basically, I think that more Drood suits wouldn't only be a visual thing, but also an actual thing that can affect your Droods performance in space or on planets. In career mode, you will start with a low-level suit that isn't that great and is only really used for getting into orbit. But as you eventually start earning more money, you can spend it on new and better suits for your Droods. I'll list a few examples of what they should do and be like.
The Starting Suit
When you start a game in career mode, this will be the first suit you get making it the default one. The suit isn't that good and is only really useful for low orbits for early game. The suit will include a short tether allowing you to attach to a craft. The suit does not include any jetpack and the tether is the only way to stay attached. The suit's mobility isn't that great on the ground so you won't want to keep this suit for long.
The Landing Suit
This suit is the next suit you unlock in career mode. It is mainly used for walking on planets or moons. The suit includes a longer tether but still doesn't include a jetpack. The mobility on the ground is better in this suit than in the starting one but isn't as maneuverable in space.
The EMU Suit
This suit is designed for space EVAs and isn't used for walking on planets. This suit is the best for EVAs and is even better than the final suit at it. This suit is the first that includes a jet pack for use. It has more fuel than the final suit you unlock and includes a longer tether. This suit has the worst mobility on the ground out of all the suits but is good at maneuvering in space thanks to the jetpack.
The Final Suit
The final suit you can buy is the current default Drood suit. This suit is the best for exploring because it has the most mobility and maneuverability. Droods are the fastest in this suit allowing them to get much farther quicker. The suit takes the best elements from the suits and combines them to make this suit the best. The jetpack isn't as good in this suit compared to the EMU suit but has a way longer tether to attach to things.
Reason to Upgrade Suits
Mobility and Maneuverability aren't the only reasons to upgrade the suits. If a Drood is wearing the right suit in the right environment you will earn extra money. For example, if a Drood is wearing the EMU in a space station, they will earn you more money because the suit is designed for that environment boosting their efficiency. Another example would be using the landing suit for exploring the moons or planets as that suit is designed for ground walking.
Unlocking the suits is very similar to buying new parts meaning you can buy them off a menu. In sandbox mode, the suits can be easily changed in the part properties menu allowing you to pick the suits you want for missions. I was also thinking that the amount of Droods that can fit in a capsule depends on the suit that the Drood is wearing but that might be a little annoying to some people.