This is an interesting proposal. However, if one can give a talk in English... why wouldn't one be able to submit the application/abstract in English as well?
I can see this would encourage peer reviewers who speak other langues natively to participate, but as pointed out this also carries the danger of the pool of experts (perhaps) being smaller and therefore there being greater risk of conflict of interest (or not).
I can also see how if presentations are made in other languages (not English) then the audience of those presentations might be reduced/othered etc.
It is a real dilemma that like many others here I keep thinking about.
My main concern is that languages are not neutral vehicles, and that research submitted for review in a particular language will not be the same research (i.e. might not have the same quality) when translated into English (and who will do this translation? if not the researchers/authors, will translators get credit and can count as academic authors? a series of problems arise...!) Unless we are talking about researchers presenting a paper ("reading a paper") in their own language and having a real-time interpreter in situ...
Do you know what I mean? Some research in, say, Spanish is not only research that could be presented in any language, but that results from the particular settings/problematics/contexts of Spanish-speaking academic cultures, availability of research, etc. Perhaps what is top notch research in Spanish is not necessarily top notch research in English, mainly because that type of research in English has, let´s say, in some cases, already been done?
Just some brainstorming in public here...
Cheers...