Regarding the mutator, a few more thoughts on that popped into my mind last night: for one, hadn't Kamek also put together a pack with placeable automated defense turrets a few years back (edit: yes, he did, see
here for more) that could be used to achieve pretty much the same goal when it comes to auto core defending? If memory serves, that content was used in his ArenaofEvil and ArenaofDarkness maps too. Also, if anyone cares to imagine how a node trying to defend itself against any hopeful suitors would feel, they need look no further than the most popular version of SlatedWorld where such a feature had been used at its primaries for years now and it didn't exactly add much to the game, if we're being honest. Oddly enough, another issue the previous two references have in common is all of those maps had post-match-end bugs that would either fail to lock players in place or even outright crash the server running 'em (mostly why everyone quickly stopped hosting the Arena maps, even though the Evil variant was a decent effort); the conclusion I'm getting at here should be obvious by now: this gameplay feature has been cursed by a powerful witch and should be left alone! If one must persist, however, why not simply opt for team-specific hurt/kill volumes to combat node/core lurking with instead of additional code that has to consume server resources every so often (or even per tick) to check for nearby enemy actors within LoS and fire a projectile at 'em? That would seem a bit more practical to me. Anyways, that's all I got to say about that. For now

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About RA2 now, oh good, you already have it. That means you're already familiar with its wacky vecs and their mechanics the game featured when it comes to considering the suitability of such ideas for UT vec adoption. You know, stuff like ray scattering to secondary, proximal targets (prism tank); inventory/arsenal-dependent variable turret vecs (IFV), dynamic area poisoning/denial (desolator). I'm not including the hovercraft transport in that list because a flying vec carrier already discussed elsewhere is a much more practical take on that idea. Also, adding the Yuri's Revenge expansion's content on top of that, one can also pick out concepts like an exclusively minigun-based armoured vec (Gatling tank) or even a mobile attracting/repelling beam platform (Magnetron); although, admittedly, that last concept has a better implementation in Half-Life 2's grav gun, but still.
Lastly, casting an even wider net over the rest of the classic C&C titles, there's a few other, equally tempting ideas that seem to've somehow failed to inspire any UT vec creator up till now; mine laying (RA1), mobile radar/comms jamming (RA1) and mobile sensoring/decloaking (TS), mobile stealth generator (TS), flying vec carrier (TS), mobile EMP vec (TS:FS) and probably a few more than are eluding me right now. Point is, there's still plenty of room and potential to expand the ONS gameplay as well as players' established playstyles in quite a few novel and interesting directions IMO, as long as creative ppl are willing to take an inquisitive look into the mechanics of other vec/unit based titles and pick apart what all was unique
and worked from the rest of their more typical content (say, all traditional tank approaches). Anyways, 'nuff rantin' for now.
Edit: I dunno if RA2 has problems running on W7 x64 (still running all my classic C&C RTSes on 32bit XP here and my brother's Win7 OS is also 32bit so I can't test that there either), but the dedicated C&C community is still quite large and with a vast enough knowledge base that I bet they'll have found ways to overcome 'em if there are. Do lemme know if I can help with anything though if/when you decide to pursue the matter more

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Kudos on the sig too!