Hi Adeline,
I hear you. I am a project manager, passed vetasses, and got an invite from SA for 489 as my occupation was only available in SA. I was also planning for 189 or 190 but no other state made project management available. I took a chance and got the invite.
I suggest you go for 489 as well. It is not compulsory to work as per your occupation. You can always do any other job. About the medicare, yes you would have to get medical insurance on 489.
The main conditions of 489 are:
Living in SA for two years (but you can travel all around Ausie land)
Working for one year in SA (you can take any occupation)
State wont insure you medically, you will have to get it from a provite company
So, for me, these conditions are acceptable as I am not sure my occupation will be available in any other state next year. I suggest you do the same and take this chance. A bird in hand is better than two in the bush.