also, the 42 days annual leave they offer in the contract are used to fulfill the companies "suggested" 24 days off in any 3 month period, so your contractually-agreed annual leave days off are going to be much less than 42! example; I took 2 weeks of leave, and got 3 days off the rest of that month, 7 the next, and 6 the next. That's 16 days off in 3 months!
also, your seniority for monthly bidding and vacation bidding ie your "fleet seniority" is based on your check out on that equipment, not your company seniority. so after putting in 5 years as FO with the company, and getting command, you go to the bottom of the bidding list for your fleet, giving way to DEC who joined the company on your fleet, 3 months ago!
I'm having a hard time making sense of your vacation example. You took 2 weeks vacation in month 1. Shouldn't that go on top of you normally scheduled days off for that month? Also, you describe 7 and 6 days off for months 2 and 3. Don't you have a minimum number of days off per month?
The seniority example you gave seems absurd. How can a new hire be senior to somebody who's been there for years? What then, does company seniority count for? I've never heard of a system where you lose seniority when you change equipment.