I'm the current curator of Weapon Rework and Expansion. I've updated it so it works with the current version of OXC and the nightlies. Look for Weapon Rework and Expansion [Debugged] on the mod portal. Mass Accelerator Weapons works under the new mod system without any modification what-so-ever. You need to place it in your mods folder instead of the data folder.
Your mods folder can be found in: C:\Users\<yourusername>\My Documents\OpenXcom\