Arena certainly has it's purpose, don't get me wrong. They can fill a server, but then, so do a lot of other larger levels.
In level design terms i don't hate arena and i have no objection to people creating them. Heck, this is a good oppotunity for novice level designers to get some practice and see what they can do without having the stresses of creating the wholey more complicated dustbowl and payload setups. Basically "the new guy" on the forums doesn't have to make an idiot out of himself by saing "i'm making a dm box map for TF2" because he can atleast turn that into something worthwhile, if he chooses to put the effert in of course.
As for remakes, they should not happen. So you think you can make something play better? Ultimately people like us have no place deciding this and as has been said a thousand times, if it is to be done, get permission. If you want an arena version of a Valve map, the most sensible course of action is to send a request email to valve, if they get enough, heck they'll probably do it; they made cp_steel official for the same reasons.
But why bother. (I don't mean why bother sending valve an email, i mean.. changing a maps gamemode).
Make your own map. It's infitinitely more satisfying, infinitely more gratifying and a respectable work effert. Going into a map and ent-editing for purposes of simply changing it's game mode isn't going to earn you salvation or respect, especially in a community like this. People want to see original work and this is to a lack of better words a customisation site, not a Valve maintenance site. We're not here to fix Valve's broken produce, or anyone elses; that's their job. We have our own job as custom level designers. Personally ent-editing someone elses map is not level design, there is no design involved and the level is already there.
If you've resorted to creating alternative game modes for existing maps by other people then you probably need the practice in making your own anyway, and if you have any intention of releasing your own map then i'd advise to get cracking; because we're all waiting in eager anticipation! These maps don't get fumed, atleast not untill the person responsible demands for a bigger response from the community than he initially recieved, thereby forcing peoples strong opinions on this usbject onto himself.
I guess the saying should go, why try to fix something that may not even be broken when you can make something new that's better.