I love Simon! Well, I love SYE-min, and I don't mind see-MOn (like the French pronunciation, however you'd attempt to spell that out). But SEE-mon... I'm not sure how I feel about that. I actually have the same problem with Edmund, my long-time, all-time favourite boy name. Where I live, Us are pronounced like "OO" and ed-MOOND sounds awful to me. And I don't like the look of Edmond. I did find Edmon, so if I have a son and still live here, I'll probably go with that, but I'm not sure if there's a similar option for Simon.
I think that if Simon with an EYE sound in it *is* possible to pronounce where you live (like someone being named Lila in North America but pronouncing it LEE-la) and you absolutely want to use it, then why not? If it's not a sound people can make easily (why Leire is not on my list as a first name. I can't see the majority of my family being able to pronounce it as anything other than "Larry") then I'd either go for a middle name spot, or drop it... or use it and deal with it always being mispronounced. I mean, people name their kids Saoirse in North America and it ends up being fine... but it might depend where you live, too, and how open people are to foreign names/ foreign pronunciations.
Simon Anton
Simon Bruno (I love Bruno!)
Simon Daniel
Simon Henrik
Simon Luka
Simon Oliver