[Xperia Play Q&A, Help & Troubleshooting] Xervils:
I first got an Xperia Play around the end of 2012. After Verizon allowed the r800x's bootloader to be unlocked I've tried over a dozen GB/ICS/JB ROMs but ultimately ended up going back to 2.3.3 due to its speed and then modifying the ever loving hell out of it. Despite being done for about eight months I've never released it, for reasons that will become obvious as this post progresses. I'm curious if others have done similar projects and would love to hear about them if so.

My ROM is called eNOS (enhanced New Operating System) which is based on the 3.0.1.E.0.88 TFT image for US Verizon r800x units. My primary goals for its design were speed, massive emulation support, free /data space and some functionality I require on a day to day basis (Exchange email, web browsing, FTP connectivity, etc). I removed all Google and Verizon services (Though I left enough for the Play Store to be sucessfully flashed via zip if need be) and a ton of other things:

Adobe Flash Player
Amazon Kindle
Android Live Wallpapers
Anonymous Usage Stats
Apps 1.03
Asphalt
Backup Assistant
Books
Browser
Bruce Lee
com.sonyericsson.capabilities
com.sonyericsson.unsupportedheadsetnotifier
com.sonyericsson.vzwsetupwizard
Crash Bandicoot
CrashMonitor
DiagMode by SEMC
Diagnostics Tools
Digital Clock (Widget)
Field Test Mode by SEMC
fotabootreceiver
Gallery
Get Games
Gmail
Google Backup Transport
Google Calendar Sync
Google Contacts Sync
Google Partner Setup
Google Search
Google Services Framework
Home Screen Tips
HTML Viewer
Keypad Programming by SEMC
Launcher 2.3.3
Live Wallpaper (Both PSP variants)
Live Wallpaper Picker
Madden NFL 11
Market
Market Feedback Agent
Market Updater
Media Server
Mobile Care 6.1.0
My Uploads
My Verizon Mobile
Network Location
News and Weather
OfficeSuite
Pico TTS
QC SEMC Service
Search Applications Provider
Service Menu
Skype Mobile
Software Update
Sound Recorder
Street View
Swype
Talk 1.3
Tetris
The Sims
TTS Service
UserAgentProvider
Visual VM
Voice Dialer
Voice Search
VZ Navigator
VZW Package Installer
VZW SMS Filter Service
Xperia Play Menu
Youtube

I bought a CM7 theme called "Matted Blues" and took the assets from v1.3 of it and integrated them into various system APKs and some third party ones as well. To conserve /data space, I integrated all my third party APKs (except for native Android games) into /system/app:

2600.emu 1.5.14
AdAway 2.9.2
Advanced Task Killer Free 1.9.7897
ADW Launcher 1.3.6 (Themed)
AFWall+ 1.3.4.1
aLynx 1.032
AndChat 1.4.3.2
AndFTP 2.8
Any Cut 0.5
Autostarts 1.8.1
Camera Mod 7 (R Trigger as Shutter [Themed])
Cool Tool 5.4.1
DMG.emu (Modified GBC.emu Free 1.5.13)
Email 2.3.4 (From CM7: Fixes Exchange/contacts data being lost on reboot and wakelock bugs found in stock Email.apk)
Emulator Shaders 1.1 (For My Boy! emulator)
ePSXe 1.9.33
EZ Folder Player Free 1.1.24 (Themed)
FDS.emu Free 1.5.13 (Modified NES.emu Free 1.5.13)
Folder Organizer 3.6.7.1 (Themed)
Game Keyboard+ 6.1.1
GBC.emu Free 1.5.13
GScript 1.0.3alpha
MAME4Droid 1.5.2
MAME4Droid Reloaded 1.2.1
MD.emu 1.5.12
Moon+ Reader Pro 2.6.8
MS.emu (Modified MD.emu 1.5.12)
MSX.emu Free 1.5.13
MX Player 1.7.31
My Boy! 1.6.0
NES.emu Free 1.5.13
NGP.emu Free 1.5.13
nostalgia.gg 1.12.1
Palemoon Browser 25.3 (Themed)
PCD.emu Free 1.5.13 (Modified PCE.emu Free 1.5.13)
PCE.emu Free 1.5.13
Power Toggles 5.0.10
Quick CPU Overclock Pro 1.4.5 (Themed)
QuickPic 1.5.3
Root Explorer 2.21.1
SC.emu (Modified MD.emu 1.5.12)
SharesFinder 1.3.6
SNES 9x EX 1.5.18
Terminal Emulator 1.0.62
Titanium Backup Pro 5.7.0
Wakelock Detector 1.6.1
WonderDroid 1.9
Xperia Play Tester 0.2
ZArchiver 0.7.1 (Themed)

To further save space, quite a few of these had any non-ARM7 .so files removed from their APKs. Then those needed were gutted from the APKs then moved to subdirectories under /system/lib/SYMLIBS then symlinked from their /data/data locations to them. There is also an initrd script that symlinks the Dalvik cache to /cache from /data.

Even with all the controls/etc configured for the emulators and such total /data usage on a clean NANDroid flash is 7MB.

Some other things:

Modified DoomKernel v2 (1.6GHz variant).

~270MB of free RAM on boot.

Disabled Autobrightness.

Bravia Engine

GPU rendering.

Under/overclocking profiles can be set by tapping the central widget on the home screen

(368MHz - 1.6GHz).

Under/overvolting set by /data/local/voltages.sh. All speeds except 1.6GHz are undervolted by at least 25mV.

Disabled chargemon: Now you can connect the phone to a charger/USB port while powered off and

have it boot normally. (Useful if your power button has failed).

100% battery/charging status bar mod.

Search button remapped to POWER, since the r800's power button is fairly fragile.

Sony Sketch EF Font.

Disabled Auto Retrieval of MMS messages to hopefully mitigate Stagefright vulnerability.

ADW Gingerblue theme icons and a bunch of emulator icons directly embedded into intitrd (/Icons).

Emulator BIOS files embedded into /system partition.

Recreation of /data/local scripts in the case of a /data wipe, as well as emulator lib symlinks.

Most programs have the INTERNET permission ripped out of their manifest files. Even though I paid for all of them, I don't like applications sending god knows what to the internet; even worse if a paid program wants to display ads.

I dumped several NES songs/SFX to Ogg/Vorbis files and put them under /system/media. The default sounds the ROM uses come from Shadowgate.

It runs fairly fast and is virtually bug free. Battery life is also better than stock and it basically does everything I want it to.

Some pictures: imgur.com