There actually isn't a lot that I would change about the ending (aside from the philosophical mumbo jumbo), but I do wish that it had been Kaidan with Shepard on the Citadel instead of Anderson. Here's my brief take on what I think should've been the final romance scene.

Shepard closed her eyes, listening to the crackling and the poom-poom-poom of missiles decimating their targets. She could almost trick herself into thinking they were celebratory fireworks. "We did it, Major."

"Yeah. Yeah, we did."

A long silence followed before she could muster the energy to speak again. "You should've stayed back with the others."

"And miss out on the view? Nah."

"Heh. Best seats in the house, aren't they?"

They fell into another lull, until an elbow eventually nudged her in the side. "To the end, Shepard. I'm right here with you. Always."

She reopened her eyes, her muscles protesting every movement as she twisted towards him. That face. She'd spotted it before–on the Normandy as he had overheard wild retellings of battling the Collectors and the unforgettable anecdotes during the crew's downtime; infiltrating the Cerberus base and crawling through the remains of the Human-Reaper; every subtle comment about how much time had passed since they had last seen each other–it always read the same way:

I wish I could've been there.

She shook her head, offering a sad smile. "You didn't owe me anything, Kaidan. Ever."

"Maybe not. I just…" A strained grunt escaped as he attempted to inch closer to her. "I couldn't bear the thought of you doing this alone." He glanced down, his hands shaking as he pulled them away from the gaping wound in his side. "Oh, god," he gasped, his head rolling back. "So…much…blood. Is it…is it all my blood?" His eyes suddenly darted about, searching for her face. "Are you…Shepard, are you bleeding?"

"Shhh, Kaidan." Please. Please don't go into shock. Not now. She firmly cupped his chin, desperate to hold his gaze steady. "It's okay. It's okay. Stay with me." She pressed her forehead against his, feeling him tremble with every shallow, haggard breath. "I'm scared shitless, too."

She sensed him fumble for her hand, clutching it against his cheek. He nuzzled her palm as she remembered how he kissed her for the first time in years; how happy he said she had made him.

"Shepard," he rasped. "Say you'll marry me."

Her eyes stung as the tears clustered, barely able to nod a yes. "Okay, Kaidan. I'll–" she inhaled sharply, voice cracking, "–I'll race you to the altar."

"You're on. No cheating with biotics, though." He sniffed back a chuckle, the warmth of his breath welcome as he rubbed his stubbled chin against her cheek. "We'll have a house overlooking the bay. You'll be lying in the hammock reading a good book; I'll be grilling steaks on the patio…and our daughter will be playing in our huge backyard."

"Daughter?"

"Yeah. Spitfire like her mom."

"If she has her father's eyes, we're in bigger trouble than the Reapers. She'll get away with everything."

His mouth formed some semblance of a grin as he nearly laughed, but it quickly deteriorated into a coughing fit. "It hurts," he panted, chest heaving. "It hurts to…" His head swayed to the side, Adam's apple bobbing as he swallowed a sob. "A-and…and later we'll tuck her in bed, kiss her goodnight…and everything…everything will be quiet. It's been too loud for so long, Shepard. Could really use another sanity check right now."

"So could I."

The gunfire had begun to subside, the once-blazing fires across Earth's surface now glowing a muted red-orange. Kaidan's head tilted downward, eyes fluttering shut. A dull ache crept up Shepard's throat as she felt his fingers slide out of her hand; she didn't have the strength to grasp them again.

"Everything will finally be…quiet."