Welcome aboard bubbykong -
I wouldn't recommend this due to the sodium content of the individual meals. Ive seen meals hitting upwards of 1500mg's of sodium and thats not the entire MRE. I know I did a review here of a Chicken with Salsa MRE and the main course was over 1000mg by itself. I forget what the entire meal came too when I added the sodium for each component together but I know it was extremely high. If you take just the main entre and average 1000mg's of sodium x three entrees a day I don't think your system is going to appreciate the sudden influx of 3000mg's of sodium. Thats just the main entrees! Add in the sodium content of the other components and you could be in for some real trouble! You may feel alright at first but once you start hitting the squats you're probably gonna feel it in the chest. If you're into hindu squats/ push-ups it won't be long before you're hitting Malox or Pepto!
Also, take the cost into account. We were all 23 once and I'm sure a lot of us were backelors. I was. Let's say a "safe" average price per MRE is $5 x three of those per day, thats $15. Average that out over a 90 day period and you'll be shelling out $1350 just for the meals. Throw in the shipping/ handling and the price per meal goes up. Now add in your 'supplemental' meals and the cost goes up further.
What you could do instead is check into memberships at bulk food places like BJ's, Costco, Sam's Club, etc. Also look at local discount places like Walmart, Dollar General, Aldi's, and even K-Mart. These places usually stock quite a bit of canned meats and increasingly they are stocking retort pouch meats just as you would find in MRE's. With a little investigating you should be able to come up with a system of knowing when each store is likely to have these on sale at '2 for $1', '3 for $4', or even '$1 each'. The only shipping/ handling you pay at those places is the fuel you burn driving back and forth.
I usually hit BJ's for their 3-packs of DAKs hams, Sams' Club for their 5-packs of chicken chunks in water, and other places. As for ease of cooking it doesn't get much easier than slitting open a retort pouch of tuna or diced chicken, squirting in some mayo or mustard and chowing down. As for the canned stuff if I don't feel like being civilized about it I just remove the label, open the tin, drop it on the burner! You can assemble your own "MRE" from readily available foods you can buy in bulk and with a lot less sodium!
Keep in mind food researchers do lots of extensive testing with soldiers at the peak of physical fitness, including blood/ chemistry work-ups, etc. While this testing will never sufficiently replicate the actual combat conditions a soldier will live under while eating MRE's it at least provides a base line from which to try and work from. When they say 21 days should be the maximum length of time a soldier subsists on MRE's, its definitely for a reason! Remember, not just intestinal/ digestive issues but the potential for mood swings.
Lastly, as for 'bulking' let me tell you there is no better place than here for comments on MRE's and bulking up. Many here have spent a portion of their lives surviving on MRE's at one time or another and many will tell you 'bulking' isn't a problem. Unfortunately, while you may start bulking, chances are that won't be muscle baby! If the consumption of MRE's for any extended length of time resulted in beneficial muscle gains most of us at one time in our lives would have looked like Hercules!
Look for off-the-shelf supplies. You'll be healthier for one thing, so your body will thank you. Take in large amounts of good, lean proteins and fresh veggies low on the glycemic index and you'll get the gains you seek. You also won't go into debt.
Hope this helps in some way. Look forward to hearing how you make out!