I would agree that Recon is the most logical class (like a Signaller asking for reinforcement) to have this tool, but I can also understand the fear of having campers sitting on their "sweet spots" and sniping the whole game. But that can be easily managed if you add timers/cooldowns. Just as an example: the "life" of a spawn beacon lasts for 30 seconds, or, you can place a spawn beacon every 300 seconds, or, the cooldown between re-spawning on beacon is 180 seconds. I am just throwing numbers here, just to get you the idea.
There is also the possibility, if the game has envisioned that type of role, to restrict the Spawn Beacon only to squad leaders (whatever class they are) and restrict the spawn point only to its squad.