orthohawk:There is no "baza principo" that allows any word (other than "la" or a singular nominative noun, as allowed by Rule #16) to leave off any letters and be replaced with an apostrophe.

That's just wrong. The rule #16 states that these words can be apocoped, but it doesn't state no other word can. The Fundamento is a basis for expansion, and creation of new rules, or even amendment of existing ones is sanctioned by Zamenhof himself.

Tangi:

orthohawk:There is no "baza principo" that allows any word (other than "la" or a singular nominative noun, as allowed by Rule #16) to leave off any letters and be replaced with an apostrophe.

That's just wrong. The rule #16 states that these words can be apocoped, but it doesn't state no other word can. The Fundamento is a basis for expansion, and creation of new rules, or even amendment of existing ones is sanctioned by Zamenhof himself.

Well, fine. Then let's just add enough verb tenses and moods and whatever we need to come up with the 500,000+ forms that Volapük has!

and while we're add it, let's add about 14 more noun cases, like in Finnish.

Tangi: The Fundamento is a basis for expansion, and creation of new rules, or even amendment of existing ones is sanctioned by Zamenhof himself.

Not since Bulonjo. Sorry.

Of course we can create new optional cases, pronouns and verb forms (like it already happened with new tenses formed with both participial and personal affixes).
See the paragraph 2 on page X of the Fundamento.

Why are we still discussing this?

Why do you think it is appropriate to come into a forum of proficient speakers and, as a newcomer, try to tell them what they should and shouldn't do with the language?

I'm not going to comment on this thread again, and I encourage others to refrain also.

Challenge: Propose your reforms in the Esperanto-language forum. Most reform proposers can't do that.

I always find these reform threads amusing. The profusion of righteous indignation and determination to take offence at any turn is truly a sight to behold!

I think at the heart of it is this misassumption, as stated in a previous posting:

"Esperanto is a constructed and much younger language. It's really up to the users to decide how to use the language."

It's true that Esperanto differs in many ways from the national languages, but it does not in any way follow that users can just decide how they want to speak, on whatever whim takes them. The time for tinkering with Esperanto has long gone, and given the schisms of the past it's no surprise that many if not most competent Esperantists are relatively sensitive to the norms and customs of established speech.

Offering up dead-on-arrival reforms like changing something so fundamental as "esti" in conversational Esperanto can't really be taken seriously, at least not as anything other than a pet project. That's not to say it has no worth, pet projects can have worth in their own right but they are unlikely to be of any interest to people who want to speak the actual language, as it exists in the world today. Surely this should not be hard to understand.

In any case I'll offer up some answers to the OP's original questions:

I'm wondering, has it ever been proposed?

Not to my knowledge, but it wouldn't surprise me if it had. People offer up all kinds of proposals for altering or improving Esperanto all the time, but they usually go nowhere, mainly because by and large they serve no useful purpose, but also simply because it's difficult for any reform to actually take off.

If so, how was the reception of this proposal?

It would imagine that, with good reason, it would have been the same as most of the others: "Yawn, heard it all before, go learn the language before presuming to offer improvements, etc".

are people using this variant of "esti"?

I've never seen it used, and I'd be very surprised if it were in any kind of use outside of poetry, or person-to-person 'fuŝparolo' (of the kind I sometimes indulge in with Esperantist friends - a guilty pleasure )

Tangi:Of course we can create new optional cases, pronouns and verb forms (like it already happened with new tenses formed with both participial and personal affixes).
See the paragraph 2 on page X of the Fundamento.

Tenses like "povintus" are fully covered by the Fundamento. No new word roots whatsoever.

As an aside, I don't think the challenge with Volapük's many possible tenses is so much that they exist, but that several tenses are distinguished by fine vowel shades, such as e and ä.

In a similar way, it's no problem to me that povintus exists. I simply don't use it.

As for "mi estas" being long, I don't mind. Spanish has many more syllables than French on average, and I like them both. It's just the flavor of Esperanto, and not some flaw to fix.

tommjames:
It's true that Esperanto differs in many ways from the national languages, but it does not in any way follow that users can just decide how they want to speak, on whatever whim takes them. The time for tinkering with Esperanto has long gone

Which is a decidedly good thing! I've been trying to learn Lojban, which apparently isn't out of tinkering stage yet, and boy, is it frustrating! So many times, I just want to yell, "All right! Get your act together already!" It's fairly small tweaks, mostly, but they add up... Hopefully it'll get the kinks worked out and stabilise sometime; I think it has a lot of potential.

(the most troublesome reform proposal being one to, of course, decrease the number of syllables...)

u reely hv sum praablmz w/ eksepting thingz in Esperanto - inglish needz e loda rifohrms tu ceptin that piple arnt gonna eksept em fohr reel n itid b hard tu unnerstanem - eye leyek Esperanto jus' az itiz n im naat gonna chehng fohr sum beginnr