In the last case, it's important to know that Fading and sustaining penalties aren't very substantial costs. Threading a Complex Form to mimic a smartlink is a great idea, except when you get into the math of it. First off, you suggested that it gets a flat +1 bonus to dice pool and accuracy per hit. Assuming the Level is still a limit, that's still a LOT of potential hits. It's too powerful. And doing a straight mimic of the functionality of a smartlink is immediately offset by the penalty you get from sustaining the complex form.
I don't want this smartlink CF to increase accuracy at all, that should still be a limiting factor. But as many bonus die as you can get hits on.
It can not be both too powerful and also having to sustain it making it too weak. I thought you didn't take the sustaining penalty if you use actions that specifically uses the CF, but looking through core, that is not the case. That means you'll need to cast at force 4 and get 4 hits to even out with the cyber smartlink. Fade values will need to take that into account. So, since 4 is the default, we want that to be easy to soak fading, meaning a level - 2 fade looks like the answer.
But looking at an equivalent spell mages get, Analyze Device and Increase Attribute, their drain values are Force -3. Those are actually far more powerful and versatile than the Smartlink CF, so we should reduce the smartlink CF more, level - 4 or 5 seems fair.
Now lets just keep with comparing it to Analyze Device, since this will be kind of similar. The mage needs to deal with object resistance, which is probably 15 dice. The TM will need to deal with hacking the device. The TM rolls software + Resonance [level] vs Will power + firewall.
A hyper specialized mage casts Analyze Device on a smartgun. Rolla 6 spellcasting + 6 magic + 2 specialization + 2 power focus + 2 mentor spirit [5 Force] vs 15 dice. And gets 1 net hit on average. He needs to soak 2 drain and on average passes that.
Our hyper specialized TM casts smartlink CF on a smartgun. Rolls 6 Software + 6 resonance + 2 specialization (and currently doesn't have any other bonuses) [5 level] vs 5 wil + 6 firewall. On average the TM will get 2 hits. This is a wash since sustaining costs the TM 2 dice.
Okay, so its not very viable at chargen. But with the skinlink echo, the TM won't have to worry about fighting his master's firewall, and with more resonance and software skill he'll be able to start to get more net hits to make it more worth wild.