While I have my doubts if it's even possible to make a structure that land units can walk on and subs can go underneath in spring.. Anything is possible I suppose..
Keep in mind I am a lobpot player not 1 vs 1..
I believe we shouldn't try bringing land units into sea, that would kind of take away what sea has, a space only a few factories have access to, which gives it a strategical factor when playing in maps that aren't fully water and have things like ponds and rivers. Besides, this structure would be outmatched by such factories instantly in situations it would be even slightly significant, both in maneuverability and the ability to hide underwater. I don't want sea to turn into LAND 2.0. Also, Djin exists for transporting units across land masses...
Additionally, I don't think making an easier way to build porc in sea would help, if anything it would make the whole experience more miserable. The biggest issue right now imo is that
it is a static lane where neither opponent can push into each other if they are good enough. Heck, try destroying
BLaNKMiND in the sea, dude is a BEAST, I can't leave lane for 2 minutes without him destroying my team, but if I stay I can't push and he can't push either, unless one of us has 2-3x the army value.
Nevertheless you got my +1 because I would like sea balance to be more discussed and ideas thrown into it sense right now it's a really boring attrition lane and in need of a new mechanic imo, because it only feels like damage control for Scylla. If you lose it then a good Scylla player will be the end of you.