The main problem I see with the repair rules is this. If I am a tech archetype I require Nuyen to improve, if I am a mage type I need Karma. As a mage, when I am damaged I just spend time to heal, and no karma - thus no impact on my progression. However, as a tech guy I have to spend Nuyen to repair/heal, and this directly impacts my ability to progress. Here are a few ideas to close that gap.
First, repair costs should not be based on full cost. It's not how it works today, and won't be that way in the future. Parts are far cheaper than the full cost of a vehicle. So I would propose the basis for any cost calculation should be the selling price of an item. In missions, this is 30% of purchase price. So repair basis, as a minimum, should be % of 30% of cost.
So going with all of Bull's suggestions above of going to a garage - start with 30% rather than full.
But lets go a few steps further. As a rigger/decker/etc I have an added cost of 1000 nuyen to my lifestyle to add a workshop/garage. That would be a lot for just a room, so it must include some basic supplies - solder, paint, tools, etc. If we make the assumption that a lot of damage will be repairable with basic parts - bondo, duct tape, some paint, etc. Then most boxes should be repairable with skill, and should be time spent with no added cost - you're already paying it in lifestyle. Provided you have the appropriate repair skills, of course. Some extended test with threshold boxes of damage, duration 1 day. (Or using a contact with limit being Loyalty for boxes repairable, once per damage - like a heal spell

)
However, life on the streets is never that easy, chummer. Sometimes tech takes a big hit. This can be represented by when the damage track passes a dice pool modifier. Each one of these can be treated just as Bull laid out above, except price is against 30% of cost * 10% per dice pool modifier, and attempts to reduce cost based on those skills and/or contacts. This is trying to find replacement parts.
Added to the last, I would suggest adding a new "Working for" category. Something like "Working for the Machine." The way it can work is you spend a week doing nothing but going to junkyards, chop shops, scrap heaps, dumpster diving, etc looking for parts. Based on appropriate repair skill(s) with Limit of Negotiation skill, they can get parts to repair the dice pool modifers. This is your ability to spot parts amid junk and negotiate/barter/perform task in trade for them. Can only do once between a mission, and any unrepaired modifiers carry over. So while rotodrone might have a "clean" damage track, some systems are damaged so it gets a -X dice pool mod for the unrepaired.
Time spent is an indirect cost - the longer down times mean you are spending more on your lifestyle. Which makes sense. It also adds in the capability of using your skills to repair or find replacements.
Some qualities like Juryrigging and Gearhead might apply here, too.