Languages reproduce themselves through families intergenerationally. That is how they work.
Failure states exist in these forms:
1. You fail to pass on your language to your children.
2. You or fail to have children.
3. You pass on a severely weakened version of the language to your children.
Barring these, a language will survive and continue. Teachers and education systems cannot replace this. They can be a tool to supplement this or assist natives and aspiring learners in some way. However they cannot function with the loss of the intergenerational transmission of authentic language. That is source and wellspring of any language.
Now with that said, I want to address and elaborate on some of your points.
Yes incompetent teachers should be punished or drummed out of the business. (In my view they shouldn't be there in the first place) Should an incompetent carpenter be allowed to do more harm than good through his crippled students? No. We can see the effects of incapable and inauthentic teaching in a language. It honestly hamstrings learners for most of the rest of their life.
Conversion courses are an idea but it holds to an unspoken premise. That one has learned bad Gaelic first. Why teach bad Gaelic first and then try to convert it into good Gaelic? I would agree though that a type of 'béarlachas busting' course would be handy to slap the bad habits out of people willing to get better. Something that all language learners must go through at points. L1 interference is a significant issue that is addressed by correction. That correction is usually specific to the learners original language background. Something like this
https://www3.smo.uhi.ac.uk/oduibhin/cruinneas/index.htm but more comprehensive and in an easy to follow book form.
Adults Adults are obviously the most motivated group and their involvement in voluntary programs and businesses should be encouraged. However in regards language inheritance. Only very high level learners can pass the language onto their children. Children under the age of 3 are the prime age for acquisition within the family. There is serious problem with this group. Children automatically and unconsciously refuse to acquire language from people who are not sufficiently proficient in it. I have observed this many times in many families.
In essence this prevents a bit-by-bit gradualist approach to introducing a language through the parents into the home. Young children are too pragmatic and won't engage with poor language capabilities unless forced.
When forced they produce useless pidgin. Personally I believe the childhood aversion to acquiring language from a poor language model is a correct and natural process. It is to prevent the child wasting massive amounts of energy on learning something wrong and dysfunctional.
Language acquisition not complicated. It is not easy but is not complicated. If it is, it is being done wrong.
Gaelscoileanna and Gaelcholáistí
They should be good. They should be great. It works in other places but not here. Now why is that?
This is purely a matter of incompetence and lack of respect on the part of schools, teachers and managers. Of course he parents are almost always very well meaning. They send the kids to the Gaelic school to learn Gaelic. However it is essentially a scam in most cases. They are not being taught Gaelic or immersed in Gaelic because their is no respect or dedication to the natives and the native form. There is far too much acceptance of failure, incorrectness and pidginry.
To me is seems like this: If I sent my son to a welding school and they taught him wrongly. Left him with terrible habits and incorrect techniques, his work littered with elementary mistakes. So much so that he essentially can't weld. I then I go to the school and see that the teachers themselves can't weld.
It think it would be safe to say that I got scammed. I was sold a bill of goods that were not delivered specially because those selling it knew they couldn't deliver it. They may be well intentioned but incompetence is incompetence regardless of intention.
In regard specifically I believe the Gaelscoileanna and Gaelcholáistí are a scam.
Ceterum (autem) censeo An Caighdeán Oifigiúil esse delendam.