You are right about the spanish input in esperanto---The reason for this,---as you have said Spanish is a relatively easy langugae to learn due to its internal logic and consistency--and this may have been the reason that esperanto was ---apparently modelled on it. in particular---spanish is totally phonetic-----once you learn how a letter is pronounced ---that it---you can read it----there are few exceptions-----this is in striking contrast to english which is a phonetic nightmare. Native english speakers have no idea what a mess the english language is. astonishingly enough many of them think its a particulary EASY and logical language---it is not. French is phonetically consistent---but grammatically too complex. This does make english an interesting language to study--in terms of its history. My understanding as to why english is so inconsistent is that it is really a Fusion language---a Germanic grammatical base with a large latin-based vocabulary, the other factor is that the english language was still evolving rapidly untill fairly recently----try reading english written in the 1500,s---very different-----in contrast the spanish of that time is virtually identical to todays as it had " stabilized" long before.
All to say that yes I think it would be a great idea to have esperanto as a common human language which despite its similarity to spanish would be a politically neutral one that would be easily learned and enjoyed by all.
Imagine being able to travel anywhere in the world and communicate fluently with whomever you met. If esperanto --or other synthetic language were universally learned it might actually be a very positive factor in helping create a common human culture and potentially lesson cultural misapprehensions.
