If you don't mind the risk of the devs stealing your design and refusing to acknowledge your work, then go for it. Not saying that the devs will do that, but various companies have done this before so it is always a risk even if there is only a 0.001% chance of it happening.
Submitting your design is a way to get a job with them or a way to get insight in how to improve your design.
I won't spoil the idea I have but the sub I have in mind to make is going to be bigger than the cyclops not 3 times just 1 and 1/2 times the size of the cyclops E.G if the cyclops is 10m long this will be 15m long but better in every way!
Sorry Kerbalatomic, I don't think there is any chance of this working as of now. The Devs have too much on their plate at the moment and even with the mesh and animations completed, there still needs to be a huge amount of work done to make a new Sub. Maybe, just maybe after the launch of Subnuaitca they might have time, but even then they will be thinking about things such as implementing multiplayer and making their own new sub for multiplayer (after launch).
The problem with letting fans design things is that they often have no concept of game balance. You summed it up in one line "...better in every way!".
If it is better than the cyclops in every way, it makes the cyclops obsolete. Dev's aren't going to be big fans of ideas that make hours/weeks/months of work worthless. The cyclops has features the seamoth does not (fabricator, onboard storage, can build in it etc) yet does not make the 'moth obsolete because it is worse in some other ways (too big, slow, power hungry, can't pitch up and down).
For an idea to have any merit in terms of game balance, it must also have such trade offs. Better in every way is bad. Better at 3 things and worse at 3 others is getting more towards the ideal. So if yours is 1.5 times bigger it should use 2-3 times the energy. If it can go deeper, it should do it at a much slower speed. If it has better visibility, it should turn slowly etc etc. The point is you must have reasons to build the 'clops in the face of your other craft, so it could not have the same features - or if it does it must do so at a much higher cost, so as to leave the preceding craft viable.
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use probably not
Submitting your design is a way to get a job with them or a way to get insight in how to improve your design.
If it is better than the cyclops in every way, it makes the cyclops obsolete. Dev's aren't going to be big fans of ideas that make hours/weeks/months of work worthless. The cyclops has features the seamoth does not (fabricator, onboard storage, can build in it etc) yet does not make the 'moth obsolete because it is worse in some other ways (too big, slow, power hungry, can't pitch up and down).
For an idea to have any merit in terms of game balance, it must also have such trade offs. Better in every way is bad. Better at 3 things and worse at 3 others is getting more towards the ideal. So if yours is 1.5 times bigger it should use 2-3 times the energy. If it can go deeper, it should do it at a much slower speed. If it has better visibility, it should turn slowly etc etc. The point is you must have reasons to build the 'clops in the face of your other craft, so it could not have the same features - or if it does it must do so at a much higher cost, so as to leave the preceding craft viable.