Well, found a very simple albeit limited solution to my quest in the freeware AutoHotkey, thanks to an amazon reviewer's comment about the $3.90 'PC remote control' [Link: amazon.com]: very easy to write little ~15-character scripts in Notepad txt files that execute whatever keystroke combos are desired (among many other more advanced functions). Assign the scripts to the four "hotkey buttons' on the remote, which execute Ctrl+Alt+1/A/F1 through 4/A/F4, and immediate problem solved. The program is very small (2mb download) and minimalist in the OS, minimizing chances for prob interfacing with other programs, and (probably most importantly) the clear tutorial documentation gets you running basic scripts in a hurry.

Amazingly, that cheapest of PC remotes also happens to provide the most Windows keyboard/commands I've seen among all others in its 36 native buttons: page up/down, backspace, tab, enter, open folder, escape, switch window, desktop, etc., along w/mouse control and basic player start/stop function.

WinLIRC and EventGhost await further exploration after experimenting with their capability to interface with my USB IR receivers and delving into their daunting documentation, but for now AHK has quickly provided my four most sought-after browser signals, with existing hardware and no additional purchases.

Oh, man, this is sweet! Instantaneously zoom in/out on web pages, switch/close tabs, all on the same single remote that controls every other HTPC function.