I have not gotten around to doing this yet in my own saga but it is a subject that I have given considerable thought. This thread contains a lot of what I have personally considered in an attempt to preserve both the forest and the value that it provides to society.
Recently I have spent a lot of time thinking about non-ritual Creo spells that create something from nothing. You can actually have a lot of fun with these and some of them are relevant to the questions you raise about iron production.
The first and most obvious one is a CrHe spell, probably of moon duration which creates a lot of charcoal. non-ritual creo spells create something that lasts for the duration of the spell and then disappears, however the effects of the created things persist. This means that magically created charcoal can be burned in a bloomery and even when the moon has passed the bloom will remain. Now actually casting this as a spell is much too tedious because your magus will have to leave their lab at least once a month probably more if they supply charcoal to an ironworking operation. It is much better to use an enchanted item that is at least semi-portable and have the covenfolk go around doing the actual creation of charcoal.
Charcoal is attractive to create temporarily precisely because it is an intermediate product in the creating of iron, thus it does not matter that the created charcoal is fake. It is also much better than creating fuelwood and then mundanely reprocessing that into charcoal. magically created charcoal also has the advantage of still requiring labor so that you are not taking the jobs away from too many mundanes who might turn angry at you as a result.
likewise if you have sufficient CrIg and rule that the guidelines for creating successively hotter fires apply further than directly specified in the core rulebook then you could create a device which heats a kiln to temperatures neccesary to: Create blooms (you would have problems with the lack of charcoal to create oxygen-carbon dynamics), fire pottery, work iron, anything that requires heat. I think that the big ones here are firing pottery and magical forges.
Another big thing that magic can do is repair things that normally couldnt be repaired. With Rego magic you can fix a broken pot or a broken iron object, kind of like in harry potter. The ability to repair things that normally cannot be repaired is probably not insignificant if you chose to apply it as a magus, again enchanted items are recommended.
There are lots of other things but these are the most relevant to what you focus on in the OP.