Option #3 was easily sell. i don't want to bother talking about the pros and cons of alloy's strategy in here, theres plenty that he can link you if you care to do that, and both pros and cons of that strategy are listed in posts in that link. not worth 2 pages.
Option #1 is pretty viable given the way your arena and team structure is built. IMO keep developing 18 year olds as a 2nd trainee each season, and keep selling those guys on the market once their salary gets bumped the following season. Keep investing in underpriced draftees and move along to the next guy. I don't think it's completely worth it to go all american, it's better to just go with the cheapest trainee that can make you a profit. I'm not sure a level 6 trainer is really necessary for this player, level 5 can save you some dough and still provide someone that is probably on track for U21 enough pops to get put on the team at that point. The one thing i'll say is that if you keep training this C, he will get too expensive for D.V regardless, it just gives you more time. Assuming you promote at the conclusion of season 22 at worst, i don't think that it will become to expensive for you to train. I've got two 20k'ish players and i'm making about 40k a week.
Option #2 is viable, kinda up to you