Nope, this will be totally fine. I have a slightly stronger magnet than the Titan in my ring fingertip and a NExT in P0 and there’s no possible way I could get those two to interact. Would have to be a few mm’s distance and that just can’t happen with your thumb meat in the way.
The flexEM has some stellar performance compared to the LF side of the NExT. I don’t think you’ll need silicon, the “edge” is rounded and not pronounced at all because of the biopolymer, but you do you.
I think a flexEM with a LF LED nail on top would perform well and be really cool. The rigidness of the flexEM would also help reinforce the weak LED fingernail, since flexing is it’s primary mechanism of failure. With the resin reinforcement though the whole implant would be very tall in the z-axis. I don’t think I would put that in my hand. Maybe forearm? There’s a good spot for access control applications near your elbow.