Hey there. If I understood correctly your project is really simple but I don't really get it on why you choose SF2 to get around doing it. Personal project? you can choose a better tool for it, unless is some homework on SF. While I "got it" I still have doubts on your explanation:
What is the project: You sign in and you find a table of 100 cells (from 0 to 99. This will never change). In every cell, there are several words (every word can only belong to one cell). These words are the same for every user.
A cell is a single piece of a table located in specific column and row. I mean
you say 100 cells, but how and where? you can have cell 0 to 99 on a single row right? or you can have the same amount of cells on several combinations of rows and columns, right?
The user can choose a word by cell (among the available words) and finally create a customized table. The available words are the same for all, but everyone can do a personal combination and save it.. In addition, a user can propose to the admin a word to integrate in a cell.
One word per cell? the easier solution would be a cell matrix, table style just like excel (rows and columns, letters and numbers), basically X/Y coordinates. Same table with same words for everyone? let them toggle select by any JS trick or just cookie playing to build the list with your front end / back end and save the coordinates as a list on a table/database. You could do that with CSV file and PHP or better: PERL. From where I'm standing is piece of cake.
Symfony? I've been playing with the framework, I don't really see how you can get around simple table positions like previous example unless you just use the table to store it and then display it playing around with JS again. I'm not an expert SF user but my knowledge leads me to where you are: too complex, more trouble than needed. What I mean is SF is a framework, nice/ugly useful/not so useful depending on the task, but as a framework it is good and strong on what it was built to do, it is not a language, that's why it sounds a lot easier to do with Perl alone or PHP.
Right now I'm just thinking about how many files I would use to build that in Perl:
1 file for the table (CSV)
1 login file script self sustained
1 file to show the data with all the JS and stuff
1 file per user to save the data OR better, one file for all the data
That's 4 files, not even 50K.
Now when I think about SF... that would be lots and lots of files, configs, routes, yml, classes and don't forget the SF cache... easy like 3K files weighting like 5MB on the cheap, am I right?