It's a reasonable question to ask of any multi-effects modeler if you can use just the effects -- by bypassing the modeling section up front. The short answer is no. The longer answer is that it's hard to turn the ToneLab LE (or any other multi-effects unit) into a true "hardwire-bypass front-end going into hi-Z-input stomboxes." You can turn off the effects, but you can't jump to the effects in a hardwire-bypass fashion. That's asking the unit to reconfigure itself electrically, which is not feasible, at least for a unit in this price range. The ToneLab LE can't be all things to all people, so it strikes a compromise. A workaround is to turn off the amp modeling or find the best "neutral" setting that suits your particular destination.
As dwerlin says, if you want no modeling and just effects, buy stomboxes (or find your own "neutral" in the modeling section). Note, too, dwerlin's comment about most multi-effects limiting you to the number/type of simultaneous effects. So buy the one modulation effect you need (in addition to the onboard one you'll use), and strap that on via the ToneLab LE's Insert Point. If you really require two onboard expression pedals and two or more onboard modulation effects (e.g., flanger and univibe), the ToneLab LE isn't for you. It puts the stress in its modeling section and in its Valve Reactor-based front end. Which is not to say it slouches in the effects dept. Vox has done a great job in the effects modeling section, too, the specifics of which I'll get into in future posts.