Heroes 5.5 WarGame Edition - Tactical Edition.

That is, it was necessary to calculate the one-time income and the weekly increase separately.

Then, the one-time income should be 100% = weekly increase, as it was in the original. Everything else remains unchanged.

which tiers and types of fortifications influenced (Fortress: on tiers 1-2, Citadel: on tiers 1-4, Castle: on tiers 1-6)

Here, in my opinion, there is nothing complicated - it is easy to remember. If this helps to avoid:

so that it doesn't turn out that the higher tiers are better in everything

Then, in this way, the early and late tiers are balanced in strength. If so, then definitely keep this innovation!