How can I change keyboard/numberpad mapping?

I need to use a lot of greek letters (alpha, beta, ect) on a regular basis, along with modifications of these. It is a pain to have to use the numpad codes every time (when working with many of my formulas, I need to put in multiple codes for the same character due to recurring accents, bars, ect), so I would like to map them directly to my keyboard to make things easier.

I have looked into some programs such as SharpKeys and KeyTweak, but as far as I can tell they only let me move one key to another, not add entirely new characters.

Windows has the Microsoft Keyboard Layout Creator, which so far has been the best alternative (I can map anything I want to any key), but it does not seem to allow me to edit the numberpad.

I can't really get rid of any functions of any other keys, so I need to map to previously "unmapped" locations. Originally I wanted to use control + (x) (for example, control + a = alpha), but because most software has so many keyboard shortcuts this has been rendered more or less impossible to practically use. The number pad seems to be the logical choice, but the windows editor does not allow me to change my numberpad.

Is there any way around this, or some other program I can't find? If I could get this sorted, it could change how work is conducted across my entire university.

That isn't really want I want. I can already get the special characters, and I do have a numberpad (at least half the time). I want to specifically map the characters to my keyboard in a special keyboard layout.

The best way to do it is any of the software out there that lets me re-map, but so far they either won't let me map to the numberpad (microsoft keyboard creator), or only let me move keys around (rather than adding something new).

If I could find a way to map new keys to the numberpad, so if I hold shift and press it I can get my special characters, those ~12 buttons would give me all the extras I need.

AutoHotkey seems to be able to do that. It can intercept most keys and send another different key combination instead to simulate a different char. I have only very little experience with it, but I think it can handle the numpad keys and replace those by alt+number combination to transform keypad into Greek alphabet.

This very likely will be what I need, it might take a bit of effort to get down (matlab is the only coding I've even touched, and even that just barely) but seems much more comprehensive than anything else I've seen. Thanks!