In fluff it is horrible to not have a decker.
In practice it is horrible to have a decker.
There is no winning.
With that out of the way, the real difficulty with the Decker and such is that they will become an interruption to the rest of play. Instead of actually participating in the group they tend to contribute very little to meatspace, and do a lot more in the matrix. Bonus points for the fact that they suffer penalties for being a mage, which is the other role you could ostensibly push to them because of their decent mental attributes.
With decking as it is, it's one of the major issues with 3rd Edition. I've seen enough rants and bile spewed on this topic that I was going to make each of those words a link, but unfortunately between age and Shadowrun Returns, some of those things are pretty hard to find now. In short, it requires a GM to run two sessions, or otherwise obfuscate the system down to a couple of rolls, which is not how it was originally designed to be played. As mentioned above, SR4 and 5 try to integrate hacking more closely into the group, but in 3rd none of that's there, and I do actually enjoy 3rd's hacking more, just on an intellectual level.
So, in short, you could try to simplify any decking down to matter of a couple skill rolls, but doing so will radically change its feel. Naturally, this may cause some people to worry about balance, but you can explain to the players that it's fair so long as NPC's follow it too; it won't cause too many issues. However, by doing so you run into issues, especially since SR3 doesn't have the same dice mechanics as, say, SR5, which can do this much more easily. Personally, I'd run these as a success test for the player to determine speed, an open test to determine their subtlety, and a success test for the system to respond with an alert or ICE, but that's getting outside the scope of this question.
Often what I do when I need to have tech in a game and can't have deckers is that I simply turn it into a modern espionage styled game with the idea being either A) plug in a thumb-drive with a virus or B) rip out the hard drive of a computer. As far as meatspace security measures, have you looked at the 3rd Edition quickstart guide? It contains an adventure which actually includes those unmonitored cameras (based on an outcome of a roll the camera may be observed). This goes for a lot of other things, though it's important to note that many of the solutions that are used to solve them (an Electronics roll against a security panel) could theoretically be applied to physical-presence datasteals and the like, just be sure to give players an apparent non-decker solution to the problem.