I would spend the vast bulk of the resources on the first XI. I would also be using our academy graduates wherever possible to be the understudy. So for instance at CB if retain two of Dawson Hegazi and Bartley I would expect Fitzwater and O'Shea to be the back up options.
If a senior pro does not fit the template we should try to move them on. Whatever Rodreguiz's release clause is we should not be afraid to trade him out rather than making an ill fitting first choice or worse still an ill fitting back up option.
With regard to the loan market I am torn. I understand that fans want to secure players on contracts in the hope of some coninuity but the plain truth is there is too much talent in the loan market for the club to forgoe it as an option. I could make a solid case for nearly half of the top 10 players in the division last season being loanees.
The three parts above that I've left from your post standaman are the most important to me. There comes a time when we have to utilise the young players and really give them a chance, albeit as first replacements and that time is now. If this season is a disaster then we will need them next, the experience will have done them good. We absolutely should not be paying backup players good money.
Regarding senior pros, if they dont fit the template then sure, sell. I'd go further, any decent offers I'd sell too. Most are coming out of their prime and haven't been playing particularly well for the last two years. You'd maybe be hesitant to let the boys at the back go but I'm not so sure they'll be suited to the defensive line Bilic seems likely to want.
We absolutely have to target loans: Barnes, Gayle, Abraham, James, Mount, Wilson...were all stars last year and I could go on. In my opinion the idea would be to get a couple of first team loanees and no more but definitely go for the best ones available on the market that you can tie down for the whole season. I'd steer clear of 6-month loans after the Barnes experience last year.