Your suggestion appears to be, instead of typing:
/roll (@{selected|dexterity}+@{selected|acrobatics}+bonusdice)d10>7+bonussuccesses
(where bonusdice and bonussuccesses are numbers) The player should be able to type:
/roll (dexterity+acrobatics+bonusdice)d10>7+bonussuccesses
This is what's "intractable" given the structure of the VTT and its system-agnostic nature. You're asking the dice engine's lexer to jump through some serious hoops here, to accommodate something you perceive to be a problem when others (such as myself) see none.
Further, the difference between what can be done now versus your proposed syntax is very, very small as far as the user is concerned. And although your proposal is simpler to use (though not by much), it would be much more complex for the dice engine than you might expect. After all, it has to support every single system as well as possible.
I'm not against players having access to their dice pools; far from it. I put effort into crafting the Exalted sheet to minimize the effort required by the player to roll the dice. Could I do more to help? Maybe, but literally the only feedback I've gotten on the sheet was to allow for up to 10 dots in attributes/abilities in order to accommodate First Age campaigns.
Based on the information I have access to (feedback on the Exalted sheet and my own Exalted games), most people aren't having an issue playing Storyteller system games. Your suggestion is the first time I've heard someone complain about the need for oh-so-many macros to make the game work.
I'll reiterate: In over a decade, from personal games with several gaming groups, to multiple different gaming conventions in different parts of my state, to online discussions of the system and the games that use it, I have never been witness to a character that needed more than one tenth of the number of possible die pools on a regular basis. (That's 26 macros on the outside, for those keeping score.) D&D 4e has 17 skills alone, and I know many people who created a separate macro for each prior to the creation of character sheets on Roll20. Add in macros for powers and such, and you had many more than 26 macros for a typical 4e character, each manually created by the player.
Based on the information released the other day, there are more than seven 4e games for every one game tagged "World of Darkness", which in turn has about double the number of games as those tagged "Vampire: the Masquerade," "New World of Darkness," or "White Wolf (Any Game)." The disparity between 4e and WoD isn't as great for the count of players who enjoy playing those games (closer to 5:2 instead of 7:1). With practical experience showing more macros on a 4e character than a Storytelling System character, what does that say about the difficulty of playing WW games in the real world, as opposed to playing them in theory?
Please take note of the fact that I said "on a regular basis," and do not blow my comments out of proportion. I'll grant that creativity or exceptional circumstances can produce die pools which are not regularly used, and it would not be expected that a player has a macro for. I've already given you an exceedingly simple solution, which the GM can implement and the players don't have to type, even once:
/roll ?{Die Pool|1}d10>7+?{Bonus successes|0}
GM: Brian! Give me an Appearance+Melee roll!
Brian: #die-roll
<Brian enters a Die Pool of 5 and 0 bonus successes>