I agree, this would be a nice feature.  
The BULLETS AND NUMBERING function could have some improvements (see e.g. also Bug 57337).

*** Bug 52348 has been marked as a duplicate of this bug. ***

*** Bug 55436 has been marked as a duplicate of this bug. ***

This issue and all the linked duplicates could be solved by adding the possibility to specify "custom numbering formats".

I imagine a "Custom" entry in the "Numbering" popup menu found in several dialogs:
- Tools > Outline numbering > Numbering
- Format > Bullets and numbering > Options

If the user selects that entry, an additional edit field near to the popup menu should get enabled, into which the user can enter the list of ordered desired symbols, separated by blanks and/or commas, like any of these:
- first,second,third,fourth
- primo,secondo,terzo,quarto
- x,xx,xxx
- *, †, ‡, £
or as in my case:
- "Generalità","RTO","RTV","Metodi"

Thank you very much for your effort!
Here is what we are currently doing with LibreOffice:
https://code.google.com/p/italian-fire-code/

(In reply to comment #4)
So, perhaps rename this bug to reflect the 'folding' of the duplicates into it? e.g. "Allow for custom numbering sequences"?

Also, one can think of specifying sequences manually (i.e. giving, for each number up to something not-so-small, a string value), but the more relevant method should be programmatic, i.e. some function of the form

string getNumberRepresentation(unsigned integer number)

Summary amended for clarity. Related Ask thread: http://ask.libreoffice.org/en/question/40211/

How to push for a quick solution?
Can I propose a bounty?
Emanuele

(In reply to Emanuele Gissi from comment #7)
> How to push for a quick solution?
> Can I propose a bounty?

Honestly?  Find a developer and pay them fair wages.  How you do this is up to you, and a bounty is good option.  However, you might have better luck soliciting the services of a small development/consulting shop in your area -- folks with whom you can talk face-to-face.  (Note that you might want to require as part of your contract with said shop that they discuss their change on the LibO development mailing list and must have their patch-set accepted into master, etc.)

The biggest item lacking in much open source development is money, so if you are motivated by this (or any problem) and have available funds, you can move this process along.  I'd certainly appreciate your efforts if you went this route.

(In reply to Kevin Hunter from comment #8)
> Honestly?  Find a developer and pay them fair wages.  

Kevin, that's not a fair comment, as almost all users of LibO (or any other FOSS I guess) do not have the kind of money available to sponsor a software developer.

Maybe if the ODF had some sort of 'donation-for-feature'/bounty bins, end-users could pool money into them - but not individually.

(In reply to Eyal Rozenberg from comment #9)
> (In reply to Kevin Hunter from comment #8)
> > Honestly?  Find a developer and pay them fair wages.  
> 
> Kevin, that's not a fair comment, as almost all users of LibO (or any other
> FOSS I guess) do not have the kind of money available to sponsor a software
> developer.

Apologies; was not meant to offend.  I thought the intent of his question was "how to get moving on this getting this enhancement in?"  And the answer to that is either "wait and hope that a core developer has time/inclination to do it", or "encourage a new (non-core) developer to do it."  In regards to open-source software, those are basically the only two options.  The bounty option he suggested is a version of "pay them fair wages".

Put differently, I don't expect him to personally fund a developer; I, like most other LibO users, am in the exact boat you describe (no feasible opportunity to sponsor a software developer).  But he asked "how to push for a quick solution", which I answered.

> Maybe if the ODF had some sort of 'donation-for-feature'/bounty bins,
> end-users could pool money into them - but not individually.

It doesn't have to be individually, nor do I think I suggested that.  Again, I answered his question as asked.  If you've a better suggestion or answer, please do share it.  If I misunderstood, and he was asking for bounty communities, I can google as well as you.  For example:

    https://freedomsponsors.org/

    https://www.bountysource.com/search?query=libreoffice

But your not wrong that it is perhaps a missed opportunity that TDF doesn't have their own version.

Created attachment 116034 [details]
Writer custom outline

More than 10 spots should also be defineable. Chinese use there version of romans numerals to track things. It is a 10x12 systems. Ten Heavenly stems, 甲[jia3]，乙[yi3]，丙[bing3]，丁[ding1]，戊[wu4]，己[ji3]，庚[geng1]，辛[xin1]，壬[ren2]，癸[gui3]，as the first level and twelve earthly stems as the second level
子[zi3],丑[chou3],寅[yin2],卯[mao3],辰[chen2],巳[si4],午[wu3],未[wei4],申[shen1],酉[you3],戌[xu1],亥[hai4]. 

The image is taken under Fedora 21. Noticed there are less buttons on the bottom than.

Note the Show at Sublevel: doesn't seem to do anything, nor does the Start at:, when entering custom entries.

Just to note that MSO up to 2016 doesn't have user-defined numbering like this, but it has common ones: One, Two...; First, Second...; 1st, 2nd...

*** Bug 103335 has been marked as a duplicate of this bug. ***

Greek numbering is discussed in https://issues.oasis-open.org/browse/OFFICE-1426

(In reply to Emanuele Gissi from comment #7)
> How to push for a quick solution?

@Emanuele: See modifying Numbertext's Soros programs, which are plain text files in a LibrEOffice installation to set arbitrary custom lists (only on your machine):

https://bugs.documentfoundation.org/show_bug.cgi?id=145239#c11