Erm, the main rule book in the section on CC weapons quite explicitly states you may never get more than one bonus attack for an additional weapon no matter how many you have. The techmarine can use his pistol to count as an additional weapon in combination with his power axe. He can't claim a second bonus attack if he also bought another pistol from the armory.
I'm invariably going to get something wrong and get smacked going from memory like this =), *but* I believe there's a good reason you find that FAQ in Codex:BT and not Codex:SM. The wording in BT properly enforces the 'two weapons' rule, rather than the wording in regular SM that effectively allows you to 'add' two weapons to what the model came with. A BT techmarine therefore has to give up his standard bolt pistol if he buys a two handed weapon. A regular SM techmarine never loses the pistol, so never has to rely on his harness for the additional attack.
A forum community dedicated to Wargamers, Wargaming 40K enthusiasts. Come join the discussion about Warhammer and Wargaming collections, miniatures, tactics, terrain, reviews, accessories, history, displays, models, styles, scales, reviews, accessories, classifieds, and more!