I really love this name, but I’m afraid people will find it pretentious or arrogant? Besides, I feel like there aren’t a lot of middle names to go with Nobel, since everything would sound like someone/something IS noble (e.g. Nobel Leo > Leo is noble). I’d love to hear your thoughts on this. 
Nobel is the Dutch spelling (I live in Belgium), but it’s pronounced the same x
it’s too much imo.
I don’t think the name is too much but I do think you might run into pronunciation issues as Nobel is spelled like the Nobel [name_u]Peace[/name_u] award and not like the word [name_u]Noble[/name_u].
oh, but I live in Belgium so I think people wouldn’t pronounce it like the Nobel [name_u]Peace[/name_u] awards, but I get why you’d think that! 
Then I think it works perfectly! Plus if they happen to go to any [name_u]America[/name_u] it’s a pretty easy fix!
I don’t think it’s too much! I personally would keep it in the middle just cause I think it sounds better there but it could be a pretty cool first! I totally understand your point of the “Noble Leo” part of it, that’s a pain but with some names it could be less obvious that others, I think something longer could pair a bit better. Here’s some middles if you want~
Nobel [name_m]Harrison[/name_m]
Nobel [name_u]Maxwell[/name_u]
Nobel [name_u]Jude[/name_u]
Nobel [name_m]Evander[/name_m]
Nobel [name_u]Quentin[/name_u]
Nobel [name_m]Hugh[/name_m]
Nobel [name_m]Cassian[/name_m]
Nobel [name_m]Cedric[/name_m]
Nobel [name_m]Aurelian[/name_m]
Nobel [name_m]Casimir[/name_m]
Nobel [name_u]Taliesin[/name_u]
Nobel [name_m]Justinian[/name_m]
Nobel is quite grand sounding but not in a pretentious way. It’s very useable.
Not too little, not too much. It’s a bold choice but it’s not silly. Something like [name_m]Sir[/name_m] or [name_u]Royal[/name_u], I think, is pretentious because it brings to mind certain qualities that are not specifically attainable. But noble, as a virtue, is a realistic quality, so I think as a name it has a down-to-Earth and approachable vibe.
As for middle names, anything would work. I get what you mean with your Nobel [name_m]Leo[/name_m] example, but the reality is that middle names are fairly pointless and rarely crop up in day-to-day life. But, if it bothers you then might I suggest going for something a bit more lengthy and/or exotic?
For example, Nobel [name_m]Alexander[/name_m] and Nobel [name_m]Theodore[/name_m] have the same vibe as Nobel [name_m]Leo[/name_m], but the similar Nobel [name_m]Alessandro[/name_m] and Nobel Theodorous seem less descriptive.
Nobel is very handsome and I think the slightly different spelling makes it usable.
Nobel [name_m]Alexander[/name_m]
Nobel [name_m]Vincent[/name_m]
Nobel [name_m]Eustace[/name_m]
Nobel [name_m]Lucian[/name_m]
Nobel [name_u]Oliver[/name_u]
Nobel [name_u]Lawrence[/name_u]
Nobel [name_m]Evander[/name_m]
Nobel [name_m]Lysander[/name_m]
Nobel [name_m]Jonathon[/name_m]
Nobel [name_m]Magnus[/name_m]
I don’t think it’s too much at all! I’ve always quite liked [name_u]Noble[/name_u], and even though I know the Nobel [name_u]Peace[/name_u] Prize wouldn’t necessarily be an association for you in your country, I think that’s an awesome association.
As far as middles go, I understand your struggle!! I too had this trouble and just ended up caving and moving it to the middle spot. I do think, though, that something like Nobel [name_m]Leo[/name_m] isn’t really too much. Really, it’s just two names, I’m just really picky when it comes to my combos so it got demoted to a middle for me. I still think it could work, though! [name_m]Plenty[/name_m] of men have been named that throughout history and I’m sure their names sounded like “noble Thomas” (or whatever).
I just think you’ll be getting references to the Nobel prizes, which are obviously mostly positive but might confuse the pronunciation very frequently. I think if the associations you want are the virtue and the pronunciation of “NO-buhl” rather than " No-BELL" then just go with [name_u]Noble[/name_u].
I don’t like the spelling of Nobel (I just think about a ‘Nobel prize’), but I think [name_u]Noble[/name_u] could work. I do think it’s a bit much, but unusual word names are becoming more popular, so if you really like it, I think you could go for it!