Regarding the rest of OF4:
- the new unit might have potential but i'm not OF on beta to test its movement properties - stats alone are underwhelming unless it moves easier than a sub - turtles, plasmas, dragons, and mantas are hardly the units i wish i could tank more hits from - and the only thing this will be more effective at tanking than a sub.
- the new barracks for the new unit is 'fine' - it slots in easily in place of one of my hover tank barracks until i decide whether i need any number of them and gives slightly more attack boost - i expect longterm it'll turn back into a hover tank barracks
- the other new buildings... i have zero cultural buildings, and zero supply buildings in my city other than sometimes crystal flower stores and blacksmiths for quests - so that leaves residential, and the House Boat may fill some spaces the others can't i guess - but doesn't feel overly special either. Overall it's really hard to appreciate much in the case of tech when you release an era in so many parts, 99% of the techs are just empty calories to eat up resources in smaller chunks anyways - not many choices of things to be 'excited' about - this phase could easily have been 4 techs that costed 3 times as much instead - might be less offensive to some who object to being forced to research techs that effectively give nothing. Furthermore, when it comes to residential/supply buildings/etc usually only one will matter in an era to any given person - which one ideally would be different depending on the person but it still leaves a high chance someone doesn't want any of the new buildings from a phase making it just an annoyance that they have more tech tree to cover for no other reason than to be ready for next phase.
- the harbor upgrade/crew members - i barely ever run the thing, this won't change that other than for a couple weeks before it comes out so that i've got enough to get to the barracks and try it out, just another empty tech to pass along the way - that said, i don't think there is anything to change that - either i need orichalcum and i'll run it, or i don't and i won't. And most of the time it'll be the latter.