Issues resolved: Hornet sliding valves have more inputs than are needed for one tank, and sliding the O-rings past any of the extras will vent your reservoir. Those extra inputs are also waiting to chew up your o-rings.
Benefits: O-rings only traverse one hole. Extra brass on the venting end will turn your valve into a piston that will push back on a trigger (as discovered by Boot), or maybe open a bolt sled (a hint at what I've been working on). It looks simpler and cleaner, and unless something breaks, a seal fails, or you push your piston through the cross section, you can't vent your reservoir.
I hate to say this, but I'm going to have to protest this.
In your current setup, your fighting against the pressure of the reserve tank. In cheesy's mod, he had o rings on both sides of the reservoir's input. This is the same basic concept zero invented. This eliminates all the pressure against the trigger. Although you say it's manageable, it can be a hell of a lot better.
The extra inputs on a hornet valve don't hurt the o rings in any way. In fact, the sharp thin edge of the brass is more likely to damage your o rings then the hornet. This doesn't vent your reservoir either, which is why there are two o rings instead of just one.
If you really want a "semi-auto valve", I'd suggest just using a hornet trigger valve. If you are unable to get your hands on one, then I suggest atomatron's valve. Using cpvc is a hell of a lot easier then dremeling and soldering brass. But thats just my 2 cents.