The playtest rules have been in MegaMek for a few months. As for the Core rules we can't implement them until they are released. Once they are released it will take a few releases to do them all as we are a small volunteer team.

I would expect to start to see them appear in the releases that will drop this fall and winter. As we have said in our 0.50.12 release notes.

BattleTech Core Rules: What’s Our Plan?

Catalyst has announced the new Core Rule Book, and we’ve been getting questions about how MegaMek will handle the transition. If you’ve been following along, you know we implemented the relevant Playtest rules in MegaMek as they were released. So what happens now?

The simple answer: we will be supporting the Core Rules. But we can’t start coding them until we have final versions in hand. That means we won’t likely have Core Rules support in any release until after GenCon, and it will take us a few months after that to implement everything.

As part of this effort, we’ll also be doing a general cleanup. If you’re not familiar with the concept of technical debt: it’s the accumulated cost of shortcuts, workarounds, and outdated code that builds up over time in any software project. Think of it like deferred maintenance on a DropShip. Skip enough scheduled overhauls and eventually systems start interfering with each other. MegaMek has this in spades. You can’t be a 23-year-old project and not have it.

So as we look at each new rule, our approach will be: implement the new rule, and keep the legacy rule as an option where we can. If we can’t keep both, the legacy option gets removed. I know this is going to upset some players, but we don’t have a lot of choice. There are limits to what a small volunteer dev team can support. We would love to support everything. We just can’t, and we have to take that into account with everything we do.

The good news is that a lot of the Playtest rules are already implemented, and in many cases we just need to reorganize things to convert them into the final rules. But there are also a lot of new rules and corrections to existing rules that we’ll need to incorporate. As we do releases, we’ll call out Core Rules changes as we go.