I have been thinking about this for a little while myself (although I am really looking at it from a Dragonstar prospectived as opposed to D20 Modern). Looking at all of those systems it is really hard to get the feel of shadowrun down using the D20 system. When deciding whether you want to use the WP/VP system or the Massived Damage system you have to think about how much combat your characters are going to be in. With the Massive Damage system every combat is going to be a life or death fight (with modern combat is), but constantly rolling fort saves verses death can get a little annoying. The Wp/VP system might allow you to survive a little longer in combat.
Also another thing to look at when you are deciding this is character class strengths. For example, magically a D20 Modern spellcaster is going to be less powerful then a normal DnD caster because the D20M character won't get access to 1st level spells until they are 3rd or 4th level characters. So that is something to think about as well.
If you are were going to use the Spycraft system, and are looking for a better magic system I would recomment the Wheel of Time spellcasting system. It is set up initially like the Mages from DnD, but there are significant differences. First, there is only one type of magic, so your mage can cast fireballs, or heal. Much like is shadowrun. Also you have to have certain feats to have access to some of the different magic focuses. Finally, the ability to overchannel is much like drain for Shadowrun characters.
Hope that helps.
Salcor
Also another thing to look at when you are deciding this is character class strengths. For example, magically a D20 Modern spellcaster is going to be less powerful then a normal DnD caster because the D20M character won't get access to 1st level spells until they are 3rd or 4th level characters. So that is something to think about as well.
If you are were going to use the Spycraft system, and are looking for a better magic system I would recomment the Wheel of Time spellcasting system. It is set up initially like the Mages from DnD, but there are significant differences. First, there is only one type of magic, so your mage can cast fireballs, or heal. Much like is shadowrun. Also you have to have certain feats to have access to some of the different magic focuses. Finally, the ability to overchannel is much like drain for Shadowrun characters.
Hope that helps.
Salcor
