If you set the unit year to 3025, all the star league extinct equipment (gauss rifles, streak srm-2s, etc) are all still available. It seems that whether the equipment is available or not depends only on the original introduction date, and doesn't take into account the extinct/re-intro dates at all. With the unit year set to 3025, megamek lab won't allow you to add stuff like the LB-20X because the intro date is later than 3025, but it will still allow you to add gauss rifles even though they are extinct.
They can still be acquired though. While production is extict the ability to acquire them is not. They still have an F rating to acquire them rather than an X. While legal to build in this fasion most GMs would not allow it for new designs. This would only be a bug if this was allowed for intro tech or your LB-20X example.
Last edit: Pheonix Rising 2015-12-24
This can probably be marked as invalid and closed.