I do not see a "strategic effect" in something like this. Also it is MUCH easier for a higher divison team, with much more money to get great staff..A level 6 staff with an affordable price for a III. division team is almost impossible.
the strategic effect of it, is that actually better isn't better. In my eyes level 6 and 7 trainers, are bad investment since many people think i need the best there ... But actually they are hurting themself with it, the extra training is very little and the absic investment insane, and through the high buying price you had to keep him till he had a huge salary.
Another strategic element is the calculation when to buy a new coach, if you pay 50k for a level 4 coach with 16k salary it is easy to see that buying him every week new is a bad decision. Keeping him 30 weeks would be a fault too, smart managers or mathematically skilled managers could reduce cost with a "perfect" timing in the replacement cycle.
The replacement cycle, shouldn't be to long to make the option to change it a valid game decision, and high level staff for low prices without the need for replacement would make it a one time decision and then forget about the "staff options"(ok maybe switching PR in the PO), and also makes low level staff unactractive.
And for a lower division team should be a good level staff affordable to continue playing and developing young talents.
you could easily do this with level 4, even U21 teams are reachable with it even when i would suggest for such missions level 5 trainers. I have a level 4 trainer, and many of the old mostly not rich team in my league too, through my bough U21 player i scanning the list for a level 5 one from time to time.