I designed 3D modells of RC planes and implemented them in RC flightsims.
I know how long Skulping, rigging and implementing for a new species takes and for 4 Species, that only need new models and use existing rigs/animations of similar looking ingame spacies, it´s not that long.
Even with a small team it would for shure not need to much work and would payoff BIG.
Such "new" species are in fact more like "skinavriants" of existing species.
I highly doubt that you are working in Gamedesign right now ...lol.
Here the reasons why, in order to the suggestions you made above.
"1. Lagoon improvements." ( ??? not speciffic enough ! Could be all from a Guppy to whole new Terraintools! .... a Dev team would just laugh about such a piont ..lol )
"2. Management improvement." ( Same as 1. ... What kind of improvement ??? giving us the option to decide the hight off "ticketrpices" to make parks more empty would need a few weeks f.e. Other than that a team would need a list of the new features that you wish.)
"3. New Vehicle Attractions (Helicopter Tour, River Kayaks, Submersibles)"
Hey cool , first piont that has a clear strukture of features that you want to see.
Helicopter Tour has allmost all needed 3D objects ingame right now. If you place more than 1 JP Heli-pad in sandbox ( say 3-5 ) you have even the "illussion" of Heli-Tours . Animation for Helis etc. is all done ! ..... To implement a simple methode that one Heli flies to Heli-P 1 than 2 than 3....and finally back to 1 would need a few weeks with most of it for testing and get rid of possible bugs.
River Kayaks would need new gamemechanics and this would need much more time ( a few months) and will for shure not happen for JWE II and maybe not for basegame of JWE III.
Submersibles ....better known as "Submarine"....and in our case here as Microsubmarines would not need new Gamemechanics, because our ROV ( Submarine Drone) HAS ALL NEEDED . All our ROV would have needed would have been a new " Microsubmarine-skin",...and even the Harbour/entrancebuilding for such tours is "ingame"......
--->Lagoonhatcheries!
So ...if Universal don´t forbit it, it would just need a few weeks to implement it.
"4. Bigger, better, more varied story driven campaign." ( lol .... thats something no body can say till we now how close the storie will be to the new Movie

! ...( ehh and "Bigger, better etc.. er all very realtive descriptions ! )
"5. Micro-exhibits (similar to walkthrough exhibits in PZ) for smaller animals such as
Compsognathus, Microceratus and Jeholopterus."
That´s an terrible Idea !!!! It would be a HUGE stepp backwards !
Compys, Microceratus and Jeholopterus are big enough to work as normal Species when you build the Enclosoures right

! ....all of them work pretty nice in small aviaries with Gyrosphere tour and Aviarie-galleries.
All I would wish for , would be normal Sound for all creatures in the aviaries and more decos like "natural looking Waterfallfountains" ,smaller plants, foggenerators and fountains that look like naturall rapids that could be placed to conect visiually shallow water of different hight-levels. If You want to walk through the aviary or lagoons, a glasstunnel as attraction would be much better and that would basically just be a longer "Viewinglogg" build on the groundlevel of Aviaries and Lagoons. ----Again ,... all Gamemechanics for that are existing in JWE II right now.
PS: A much better option to get a Ride that drives in shallow water would be to implement that Gyrosphertracks could be build in Water too ! That would need a few weeks to work it out, but wouldn´t need new gamemechanics like "Kayak-Tour".