I'm all for making changes to the infiltrator.. but this is not one of them. I think having two of them gives us plenty of room for havoc wreaking. If you think two isn't enough, try some Pizza Delivery tactics with a Stalker cloak. It will make you smile.
Engi with the utility pouch can carry more mines. You can use this option if you're just placing them defensively. Edit: upon further review, it costs 3,100 certs to be able to carry that third AI mine. That's a bit excessive.
I'm not for being able to carry more mines for free.... but I would enjoy to have the option of the utility pouch
I'm all for buffing our favourite stealth class... but this is too much power for one man. (Besides, you can place two then ressupply and carry 2 in reserve)