Best just to go with 3 RL-20s and a RL-10 though.
It's situational. If I were forced to send a lance of Stingers to skirmish or delay an oncoming force expected to contain conventional units, I'd issue them iOS-LRM-5s loaded with T-Aug ammo. Lay the minefields in a good spot, and you either force them to go around(possibly through very hindering terrain), or force motive crits(good chance of REALLY slowing them down. Then I'd have them fall back to whatever pack mule accompanied them and have them pick up an RL handheld, for a single harassing pass as the remainder, going for even more motive crits.
Then they'd be under orders to retreat. Mission's probably accomplished, or they can't do much more without near-suicidal tactics.
Another idea(that actually got published as a handheld for the Axeman) would be a Fluid Gun handheld with a single ton of ammo. When an enemy approaches a city you're holding, break out the super soakers and have 'mechs lay down oil slicks while falling back to ambush positions. You'll have enemy 'mechs
literally sliding right into your traps, and without having to strip guns from your 'mechs for the squirters. }:)
Long story short: I don't see handhelds as adding firepower, I see them as adding flexibility and tricks up your sleeve. Much like OmniMechs, they make your force unpredictable, so your enemy can never know what you're going to use against him, even if his intel tells him exactly what 'mechs you have.