I think that this arrangement....

I think that this arrangement....
 

Supongo que me gustara una versión mas formál y otra mas común. Me pregunto si sea mejor usar el futuro subjuntivo para el verbo segundo- "sucediere" .

There's no reason to use the subjunctive anywhere here, and the future subjunctive is nearly obsolete in modern-day Spanish.

Your second quote should be something like this:
Creo que este acuerdo/asunto saldrá bien. Pero si no es así, no me enfadaré.

Gracias Sr.. Also just so that you can correct me further, I had thought that the default for a substantive clause (que...) was the subjunctive. That's why I used gustara (past subj.) and sucediere (future subjunctive). With the sea, that I thought was in an indirect question, which I thought could take either the subjunctive or the indicative depending upon the certainty (I wanted to communicate uncertainty there). And then for Pero si no [funcionase], no lo me turbaría. There I wanted a Future Less Vivid Conditional (I was thinking less certain than the Future More Vivid which you generously wrote.)

A few good places to read up on the use of the subjunctive to express uncertainty using «suponer que» can be found here or here.

There is hardly a case where I would choose to use the future subjunctive (unless you're quoting from law or older literature where it can appear).

I think/predict that this arrangement will turn out well. But if not, I wont be upset.

Creo/Preveo que este arreglo/acuerdo/entendimiento dará buen resultado, pero no me sentiré contrariado si no lo hace.

Espero que lo nuestro dé resultado, pero si no, no me enfadaré/enojaré.

Gracias Señores. Creo que en el futuro, querré leer la literatura vieja y contemporánea.