While MIG is used by a few companines- American Champion Aircraft, RANS, Maule to name a few. The method, set up, wire and stitch pattern is completely different than standard MIG welding. Even with the correct methods the welded cluster is 10% weaker. Now it can be easily said that the cluster at 90% strength is good enough, and I won't go into that rabbit hole.
But there will also be areas that simply can't be mig welded. i.e.- to thin, to tight or requiring movement (hinge parts) so you will need gas or tig there.
Lastly the HAZ (heat affected zone) can be a real problem done wrong with MIG, causing brittle or breaking clusters right at the welded edge.
In summation, if you have the perfect teacher, willing to show you exactly how this is done, and willing to spend the time with you for this one job, and you can get the right wire in very small lots, and can run .023-.025 wire, then go for it. If not, it may cost you far more in time in the long run as well as other un-intended results.
