I think /tick freeze should be able work through command blocks.

Put the summary of the bug you're having here

What I expected to happen was...:
I expected the "/tick freeze" to work on command blocks

What actually happened was...:
It didn't work on command blocks

Steps to Reproduce:
1. write "/tick freeze" in a command block, but activating it wont work

 

I don't know if it's a bug but long story short it would be quite cool to make it accessible for command blocks for maps and such.