Even if it was that simple, and providing you can actually answer those questions reasonably well, the conclusion from that answer never leads to a 100% perfect solution. You are either overspending or taking more risks than you should because you never know what the future actually brings. Simplifying the issue doesn't get you anywhere.
E.g. the Netherlands 1995
1. air defence, combat air patrol, close air support, humanitarian help, all within UN framework
2. NATO tasks including all of the above.
3. No current or nearby enemies, but the situation in the Balkans faces us with MiG-29, SA-2/3/6/7, ZSU-23, any humanitarian missions will be threathened by RPG/MANPADS.
Now, how would I conclude from this that I need AH-64Ds and CH-47 Chinooks in the first place. Okay, they had a vision for it and saw the future, but who would have guessed the Netherlands would be fighting in Afghanistan 10 years later...? Luckily the AF bought the right equipment (or at least to some extent), but the army didn't...
But you are right, asking simple questions does provide some framework to look at a country's defence needs. But future needs depend on vision and development in both technology/economy as politics/demographics, same for future enemies. Threat analysis combined with risk management are needed to competently answer just those 3 seemingly simple questions.
Anyway, enough about that pls, there's too much to it. Let's get back on topic: MiG-29 upgrade - Bulgaria finally does it
Any info on the upgrade? I suppose it is similar to the Polish/Slovakian MiG-29 upgrade: approved overhaul plus replacement of some Russian systems with NATO-compatible, as far as I know, only radios and IFF systems. Maybe GPS as well? Not much else, right...? The overhaul is just prolonging their lifes and bringing the non-airworthy examples back to the air. It's a very basic upgrade, nothing near the extend of SMT or Western MLU programs. Also, I am not sure, but I think at the moment there's no firm contract in place to upgrade all remaining MiG-29s, I don't remember but it was something like less than 10, and an option for the remainder... as previous Bulgarian / RSK MiG upgrade deals were unsuccessful, they've been a bit careful.
Serbia is also overhauling its remaining Fulcrums btw, all five of them if I'm not mistaken.