Even before the release of Solaris Act 3, I was debating which approach to take for the subsequent 4.0 version. Do I continue the fighter-centric, story focused gameplay of previous releases, or should I exercise my creative muscles on something new?
The choice became clear when I updated my eight-years-obsolete knowledge of FreeSpace Open and looked through what had been implemented over the last few years.
Animations!

Particles!

and curves! Even the tonemapping lighting system (including glowpoint lighting) implemented years ago had only been given a cursory glance.
I wanted to try a new mission design philosophy that moved away from the heavily curated set pieces of the previous releases, focusing on more dynamic, freeform gameplay - using systems, rather than events as the foundation. I figured modders now had enough tools at their disposal to build RTS-lite gameplay elements.
Besides, I had balanced ships and weapons in Solaris as though it was an RTS

So I'm planning for the next release to focus on new gameplay systems, such as implementing capital ship gameplay using a Lua script by (the absolute Chad Lad) Asteroth as a baseline. Embedded below are some very early WIP videos made soon after the release of Solaris 3.0, playing around with cruiser/large ship gameplay.
I've also been tweaking ground gameplay mechanics using another Lua script by Chadsteroth that lets you play missions in 2d, simulating vehicle travel. The glowpoint lighting and tonemapping systems can give some visually impressive results, and the smaller scale makes the world more intimate, more human.
The script can be used to simulate aerospace flight quite nicely, and the plan is to have these multiple gameplay types coexist seamlessly on the same map/level. The helicopter flight in these videos take place on the same map as the motorcycle scene, cruising high above the same roads that the player had been driving along previously.
Finally, I had been using Asteroth's capship command script for deeds not even he had expected: Tank Gameplay
It seems Lua scripting is a pathway to many abilities, some considered to be unnatural.

The other huge gameplay system that I've been implementing is courtesy of an amazing script by the inimitable CRZgatecrusher that lets you call in reinforcements using a "Command Point" resource system. Even more incredibly, he's implemented an AI system that uses the same callin system and commmand resources, with the ability to tweak various parameters of the AI.
The plan is to have this all taking place in one giant 64x64km level, but will require the use of the new Props system in post-FSO 25.2.0 builds. Without this feature, the limit of 500 ships in-mission at a time would be an insurmountable obstacle to making it work.
However, you don't have to wait until the next stable build to give this a try for yourself! I am hoping to have a limited gameplay demo coming out soon, showcasing the unit call-in and command system for others to try out and tinker with, and hopefully see more systems like these in other FreeSpace mods!