Just upgrade the car. The price has came down a lot with many then-options included. New motor / suspension, HW3, all the good stuff.
All depends on how much you paid for the 60D X, at the time the 60D X was priced from £64K - that pretty much the same price as a optioned up Dual motor Model 3, but your getting a much much more substantial car, FWDs, Paranomic roof all included.
In the UK I got one of the first (and last) 60Ds with AP2, build date was Dec 2016 with delivery in March 2017.
With 6 seater, white premium interior, cold weather pack, AP2.0 but I didn't pay to activate the car, the cost of our car was £71K.
I have since paid £300 to upgrade the stock speaker, £4900 in the recent FSD 'sale', and £100 for DIY HEAP filter retrofit, when available I will also order the CCS retrofit/adaptor here in Europe as CCS chargers are getting very common.
That will take my total spend on the X to £77K, the same car today in same spec is £92k for SR or £101K, that's excluding the 22inch referral wheels our X is currently wearing.
Sure who doesn't want more range, faster 0-60 time, but a new X is no way worth 20-30% more than our X, that's before factoring in deprecation.
I actually was 'forced' to pay the £4000 to 'upgrade' our 60 to 75 due to an insurance issue, and in reality the extra range has made 0 difference as daily I still only charge to 70%.
Looking at what Tesla have added to the X since 2016 with over the air updates I'm pretty happy with our X, faster 0-60 time, now faster charging, soon CCS compatibility here in Europe and hopefully at some point the new FSD computer. I cannot think of any other car I have ever bought that have had so many updates post purchase.
Throw in free for life unlimited supercharging and connectivity, our X is a 100% 'keeper', last weekend it hauled 4 adults, 2 toddlers + luggage, over 100 miles coming back from the airport - The trip in the car was so much nicer/relaxed than the plane. Upgrading to a newer X would offer the identical experience with the added bonus of having £50K less in the bank account.