I am fairly sure that bye scoring is based on best 18 players from your 22, so there would be no requirement to have two rucks playing (albeit extra numbers can be handy, and there’s no point having 11 M only players playing - ie having a positional spread is much more useful).
Historically the plan (using SC prices - but the DT concept is the same) was to try to turn two mature rookies worth around 300+k each into a new decent rookie at just over 100k, and a premo at 500+k. If you can do that every week for a while, you improve your on field side by perhaps 30 points per week for several weeks running, and that can build a lot of extra points.
It can be easier said than done though, and if the rookies don’t oblige (either by producing 300+k prices, or in a second wave of them appearing exactly when you want to downgrade to them), that can make it a lot harder, and you kind of have to delay the process by a week until enough cash is generated (eg 2-3 downgrades for 1 upgrade). Two 250k rookies doesn’t really buy you much of note.
Boosts help to alleviate that, because you can do 2 down, 1 up in a single week and you don’t lose time. Obviously there’s a limited number of them though, so I’d probably look to use them when you need to to ensure you can execute a proper upgrade (ie where you would otherwise have to delay, or choose a lower quality upgrade target).
I wouldn’t suggest rotating premiums from now on, unless you’re confident you don’t need those trades to upgrade your team. There might be scope for 2-3 based on the extra 6 trades we have, but they’re kind of luxury trades if you’re rotating premiums. Fortunately most upgrading should be done by the byes, so you should have clearer visibility on how much of a trade buffer you have by the time you can potentially use it 🙂