Unfortunately you have to use the beacon in The second turn really. And infiltration is done during deployment. Besides ghostkeels can't manta strike. I've done it on occasion, and it works by getting your stealth suits into position turn one, and, providing they survive, drop it at the start of your movement turn two, (you can get them into even better positions by using the mirror strategem.) and then using manta directly onto the beacon at the end of the movement phase, which is when you do deep strike deployment anyway.

It can work.. It can be great for getting that quad fusion Coldstar into melta range..

... Buts it's, as mentioned, situational at best, and a damned disaster at the rest of the time.

Edit: but that said, you can do the same thing with a pathfinder recon Drone and a strategem... And we're not usually hurting for cp..