In my view, I think it would be a good idea to create an "expert vegister", as you say, where the expertise of each developer is clearly defined. This tool will help you to organize the team in the project and in the future ones.
A skills inventory is a good idea when dealing with a large group of diverse skills and limited supply to meet demand.
I'd keep it simple - a table with the skills in the columns and people's names in the rows. Folks can indicate their skill with a 1-5 scale, and if they are interested in learning a skill they can indicate that with a different symbol.
Thanks everyone for your answers ! This helps me a lot.
@Kiron : I like your idea about a skills register ! It has many benefits. Only risk I think : that resources perceive it as an intrusive way to monitor their performance. But I will definitively speak about your model in next meeting with my hierarchy.
@Mirko : thank you ! I am still studying the PMBOK right now. Your remark makes sense. I need to have a look in this section. Saving Changes...
I agree with Kiron's idea and also the risk mentioned. This may not be shared with all team members. However you can use the register for many purposes such as
(1) Whom to discuss while planning?
(2) Check which skill set needed for the project is missing or not adequate and plan the training if needed.
(3) See where you have more dependency and plan to up skill others since having dependency on one or two resources will be a risk.
(4) Can use for performance evaluation on whether the performance was according to expert level and if not what are the areas of improvement. Saving Changes...