Developing your own modular autorig system takes time. There are actually quite a lot of resource if you are willing to break a rig and study. Below are some of them.

Character Rigs & Community

• Stewart by Animation Mentor
• Alpha/Beta/Delta by Agora Community
• The Zoo by ProRigs
• Toy by ToyRigs
• Ramon Arango
• Neka by characterRigs.com
• Agora.community
• Animator’s Resource Kit
• AnimProps
• Character Rigs
• Truong CG Artist gumroad.com
• Maya Rigs animationmethods.com

Modular Rigging tools

• mGear
• Hive Autorigger
• dpAutoRigSystem
• Mutant Tools
• Trigger
• Rapid Rig
• Autorigger
• Kangaroo Builder
• Mansur Rig
• Stoyan Dimitrov
• Jan Zgiet

Quadruped Animation

• https://danielfotheringham.com/quad-blog-beta
• https://vanat.ahc.umn.edu/gaits
• https://www.schoolofmotion.com/blog/how-to-rig-quadrupeds-animation
• https://boneclones.com/