Ok, this morning I fired up the neuron and I thought a little bit of this thing of the playable units problem. Given the fact that technically you can create new units just making the 3D model and properly creating the objects in the database (i.e. no dll or exe modification), you can make the newly created unit playable just "overwriting" an existing playable unit. In the process you do not alter any dll or exe. Of course, you will have to use the same interfaces of the playable unit you've just overwritten. But you can modify the sensitivity of the sensors as you like, you can modify the diving depth of the submarine or the maximum speed of the surface ship, and so on. What you won't be able to do is change the weapon load out or add/modify launchers to the playable unit.
This is a limit but still you can change a frigate with a frigate, a sub with a sub provided that they have similar load outs.
You are just modifing the database. Now, in my humble opinion, this is not only possible but also legal. I remind you that other mods, like the famous LwAmi realism mod, do modify the database. Therefore, if the modification of the database is legal and accepted by SCS, then it's possible to change (mind you, just change, not add) playable units. If, on the other hand, the modification of the database is illegal and not accepted by SCS, then also mods like LwAmi are illegal. Since the above mentioned mods like LwAmi seem to be accepted, it just seems logical to me that also the possibility to change playable units should be accepted.
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