Knocking out enemy sensors is a very viable strategy, but there are several issues with this plan. First, there's a "minimum stealth size" tech line, and to make a useful stealth fighter, you pretty much have to max it out. If you do that, at a cost of (IIRC) several million RP, you could make a fighter with the radar profile of a size 6 missile, which is pretty sweet, and would easily get you within missile range undetected by enemy active sensors, but I don't think I've ever gotten that many RP total in a game. The second problem is that NPR ships all have sensors. It could be useful against some player race fleets, but I for one always put small backup sensors on every warship for exactly this reason. The third problem is that there's no way to stealth through an enemy countermissile envelope. You can't reduce your sensor signature below that of a size 6 missile, so if you're close enough to cut down on his countermissile fire, you're close enough that he can shoot you with countermissiles - which is deadly to fighters. The fourth problem is that knocking out sensors with missiles generally means maiming the ship, which tends to take a lot of missiles. You might get lucky from time to time, but a small force of stealth fighters generally isn't going to do the job.
The only way to take out sensors without needing to blow up huge chunks of the target ship first (or getting lucky) is to use high-power microwaves, which specifically target electronic systems - sensors, fire controls, and ECM/ECCM. It's a great way to keep enemy ships from shooting you, but high-power microwaves are expensive and short-ranged beam weapons, and, while they ignore armor, they are stopped by shields. A strike group of stealthy FACs with HPMs could potentially stealth in, rush through countermissile range, and cripple an enemy fleet, but you'd have to expect losses. Can't put much armor on an FAC, especially if you need to keep the radar signature down. Plus, you'd still need a lot of minimum cloak size tech to work, albeit not as much as for stealth fighters. HPMs can be a very viable complement to a more conventional beam armament, but getting small ships to beam range is a tricky and inevitably casualty-heavy proposition. (Well, unless the enemy fleet has no countermissile or anti-FAC ships, which does happen sometimes.)