Ronny, welcome to the CT.
More dictators, now including even more obscure tyrants:
No argument with this, but any new dictators/rulers should have the flavor of the geographic locale of our beloved "hell hole."
Many of your suggestions for dictators... do not.
A greater control over vote rigging. Meaning that you have the option to only include YOUR name on the ballot paper. It will ensure victory but lead to almost instant condemnation from America.
I fail to see where this would be of any value to Trop3.
Please explain to me, why you feel that it will improve the game.
Dictator specific scenarios. Basically, you will have to weather the numerous problems that certain despots have ad to deal with. Like assassination attempts and murky business deals.
Ah, a man (I assume) after my own heart

Ability to kill political opponents who are in jail.
- Different killing options for political opponents. Have them murdered in their beds or executed publicly.
- Public backlash when certain characters are killed. For instance, if your men murder a nun then your people will be up in arms.
While I've been known to "remove" pesky irritants, I think you are in to killing... more than is appropriate or necessary for Tropico.
Greater control over propaganda. Dig up dirt on faction leaders and put it in the newspapers.
What purpose would this serve... in-game?
Political Purge edict. In order to reduce the chance of a coup you can purge your political party and armed forces for any traitors. It will make your posistion more secure but leave you open to invasion because of the weakened state of your military.
Unless political parties are added... no need.
You can already "purge" the factions and army.
Invasion from whom?
As well as having to contend with the US and Russia there should be two other factions to deal with. The Papacy and the Middle East. A good relationship with the Pope allows for strong diplomatic support that will warn off Russia and America. It will also gain you support from the many Christians on your island. The Middle East exists as a faction but cannot be controlled or directly appealed to. It basically reflects the modern day terrorist situation. If you run a moralistic regime and enact prohibition laws then terrorist groups will flock to your country, setting up camps that cannot be interacted with. This will keep you safe from terrorist attacks but earn you the wrath of America.
However, if you are too friendly with America and run a very liberal regime then you will be informed by the secret police of militants within the country and you may find a building being destroyed suddenly.
Either way, there is no way to control the situation. It is an evil that simply exists within the game world but only in a small, sporadic fashion.
The Papacy I can go with.
It has a historical basis to build on.
Middle East terrorists

This is 1950... for God's sake.
Options for demonstrations. If your people hold anti-government rallies you should be able to decide whether to allow them or have the protestors arrested. Letting the demonstrations go ahead can lead to a full scale revolution if discontent is powerful enough. But cracking down on it enrages the Americans.
You can already arrest and imprison dissenters.