I am sure I read somewhere (I think it was 6th edition) that temple guard were spawned as temple guard, stronger saurus with the abilities and duties to protect the Slann (which explained why they couldn't take or be given spawnings).
Again (like so many things), I wrote a rule set and fluff for them, just like the 6th edition wood elf book, you could make a lord and hero level temple guard with a single upgrade, which gave them a stat and rule boost, but at the cost of losing the options for taking spawnings and mounts (this included access to magic items/weapons only available for temple guard).
This I wrote to tie in with 6th edition rules and stats for Lizardmen.
An upgrade looked like this:
Scar Veteran: 30pts
+ 1 WS, I, LD and increase to scaly skin save.
Cannot take spawnings, or be mounted.
Stubborn.
Comes with light armour and Halberd.
Old Blood: 45pts
+ 1 WS, I, LD and increase to scaly skin save.
Cannot take spawnings, or be mounted.
Stubborn.
Comes with light armour and Halberd.
Both may take Temple Guard only Magic items (can have a look for them, if anyone is interested, including a very nasty magic halberd that does some very nasty things to enemies with ward saves, the greater the ward, the nastier the stack....let's just say a 3+ ward becomes a huge handicap against this weapon).