this so often gets neglected or forgotten in discussions about the whole bolster conundrum, yet the price tag it is one of the most straightforward ways to adjust the timing/power level of the upgrade. of course it does result in a sudden power spike, but so does the first tank hitting the field. and as long as the cost is adequate both will mutually delay each other and force a tech decision to be made.
of course it can be argued that 5-men sections trade a bit too cost efficient at the moment, especially when hitting a critical mass, but this could also be offset by proper pricing, e.g. by implementing a higher reinforce cost after the upgrade to make 5-men sections slightly less economical.
this, your comparison to the power spike that comes with the arrival of a tank is exactly what I meant.
But why go to all that trouble?
Why not use the same system already implemented?
Simply make bolster increasing the entity available without actually providing the entity similar to PG/5 men/6 AssG/ 7 men conscript.
That would make Pre and post bolster units have the same cost efficiency.
Why is it more trouble to increase the price of bolster than to completley change the way it works.